Healing

Akoya pearls are saltwater cultured pearls grown in the akoya pearl oyster, Pinctada fucata (martensii). They are an organic gem made of nacre, not a mineral. Japan and China produce them, and to a lesser extent Vietnam; most are white or cream, the colours many buyers think of as the classic pearl.

Amazonite is the green to blue-green variety of potassium feldspar, usually microcline (the name is sometimes also applied to green orthoclase), with the formula KAlSi₃O₈. Its color is usually attributed to small amounts of lead. It is also called Amazon stone (amazonstone).

Amber is an organic gem, not a mineral: fossilized resin from ancient trees that hardened over tens of millions of years. It is an amorphous mixture of organic compounds, usually yellow to orange or brown, and is valued especially for trapped insects and plant fragments. Younger fossil resin is called copal.

Amethyst is the purple variety of the mineral quartz. Its color ranges from light lilac to deep royal purple, and it commonly shows color zoning. It is mined and can also be grown in a laboratory.

Angelite is a trade name for a translucent, light blue-gray, fine-grained anhydrite (natural calcium sulfate, CaSO4) from Peru. It is a natural mineral, not a separate species: mineralogically it is anhydrite. It is soft and is mainly cut into beads, spheres and carvings.

Apatite is the name of a group of natural calcium phosphate minerals, not a single species; most gems sold as apatite are fluorapatite. It is the reference mineral for hardness 5 on the Mohs scale. Transparent crystals in blue, blue-green, green, yellow and violet are faceted, while translucent material is cut as cabochons and beads.

Aquamarine is blue to greenish-blue beryl.

Aragonite is a natural calcium carbonate mineral (CaCO₃) with the same chemical formula as calcite but a different, orthorhombic crystal structure; the two are polymorphs. It is the second most common natural form of calcium carbonate, metastable relative to calcite, and often converts to calcite over time. It is also a main constituent of pearl and shell nacre and of ammolite.

Black labradorite is a trade name, not a formal mineral variety: it is used for natural labradorite, a plagioclase feldspar, whose body color is very dark gray to nearly black and which shows labradorescence, a flash of blue or other colors at certain angles. Geology.com notes that much gray to black labradorite with good labradorescence comes from Madagascar and Russia. The Japanese retailer Pascle uses the name for labradorite with a near-black base color.

Black star aquamarine is a trade name for natural beryl that looks dark brown to black because of dense, oriented inclusions, mainly of the iron-titanium oxide ilmenite, in an otherwise very light blue or pale green aquamarine host. The oriented inclusions give a sheen (schiller) and, in cabochons or beads, can show a six-rayed or even twelve-rayed star. Gemologists usually call it black beryl or star beryl; the dark appearance is linked to the inclusions and the brown colour zones around them, not to the pale aquamarine body colour.

Black tourmaline is a natural mineral, usually schorl, the iron-rich sodium tourmaline and the most common member of the tourmaline group. In the trade black tourmaline is sold as schorl, and the Japanese laboratory association AGL lists "schorl" as an alias of black tourmaline. It is common in granites, pegmatites and metamorphic rocks and is rarely used as a gem.

Blue aventurine is a blue colour variety of aventurine, a natural quartzite or quartz rock whose platy inclusions can make it glitter (aventurescence); included dumortierite, a blue borosilicate mineral, produces the blue colour. Much blue material in the bead trade shows little sparkle: the Japanese retailer Pascle says its blue aventurine is for that reason also called blue quartzite. It overlaps with dumortierite quartz, and blue quartz-based beads may also be dyed.

Blue calcite is a descriptive name for natural calcite (calcium carbonate, CaCO₃) with a blue colour; it is a colour variety, not a separate mineral species, and natural blue calcite is described as relatively rare. Its colour cause differs between deposits and remains debated: studies have linked it to defects from natural radiation, to transition metals such as iron, chromium, nickel and copper (Central Anatolia, Turkey), to copper in cave deposits and to trace elements in calcite from Madagascar.

Blue fluorite is the blue color variety of fluorite, the natural calcium fluoride mineral CaF₂. Blue crystals are less common than purple, green or yellow ones. Studies link the blue color mainly to yttrium-associated color centers (an yttrium ion paired with an anion vacancy holding electrons); Geology.com notes that trace yttrium substituting for calcium can cause it.

Blue lace agate is a natural variety of agate (banded chalcedony, a microcrystalline form of quartz, SiO₂) with pale blue and white, lace-like banding. For several decades its primary source was a single mine in southern Namibia, the Ysterputs Mine, which operated from 1962 until January 2017; similar material is known from a few other places.

"Blue moonstone" is a trade name for natural feldspar that shows a blue sheen; it is not a separate mineral species. GIA describes the most prized classic moonstone (orthoclase with albite layers) as colorless and nearly transparent with a vivid blue adularescence, known in the trade as "blue sheen". Material from Tanzania sold as blue moonstone in the mid-2000s was identified by the GAAJ laboratory as peristerite, a sodium-rich plagioclase feldspar, so the name alone does not tell which feldspar a stone is.

Blue tourmaline is a natural mineral: the blue color range of tourmaline, a group of closely related borosilicate mineral species. GIA uses the trade name indicolite for dark violetish blue, blue or greenish blue tourmaline, and Mindat describes indicolite as a blue gem variety of tourmaline, usually but not always elbaite or fluor-elbaite. Vivid blue tourmaline colored by copper is sold separately as Paraíba tourmaline.

Charoite is a natural purple mineral, a complex hydrated potassium-calcium-sodium silicate (with strontium, barium and manganese), named after the Chara River area in Russia. The gem material is actually a rock (charoitite) made up mostly of fibrous charoite, which gives its swirling lilac-to-violet patterns. Its only known source is the Murun Massif in the Sakha Republic (Yakutia), Russia.

Chondrites are stony meteorites, natural extraterrestrial rocks named after the chondrules they contain: small, nearly spherical silicate droplets that formed in the early solar system. At over 4.5 billion years old they are among the most primitive rocks known and have never been melted. They are the most common meteorites, about 86% of all meteorites recovered.

Chrome diopside is the chromium-bearing, intensely green variety of the natural mineral diopside (CaMgSi2O6, a pyroxene). Chromium, typically about 0.5% and up to about 2% as Cr2O3, gives it a saturated green similar to emerald. Gem material comes mainly from Yakutia (Sakha Republic) in eastern Siberia, Russia, and is usually cut in small sizes because larger stones look very dark.

Chrysocolla is a natural hydrated copper silicate mineral, (Cu,Al)2H2Si2O5(OH)4·nH2O, of secondary origin, coloured green, bluish green or blue by copper. Pure chrysocolla is very soft (Mohs 2.5 to 3.5) and crumbles too easily for cutting, while chrysocolla mixed with silica, such as quartz or chalcedony, is much harder and is a popular jewellery stone. It is often mixed with malachite, turquoise and other copper minerals.

Crackle quartz is treated natural quartz, not a separate mineral: the quartz is heated and then plunged into water, and the thermal shock fills it with a network of fine internal fractures ("quench crackling"). The fractures can show iridescent colors and also let dye enter, so crackled quartz is often dyed, sometimes to imitate more valuable gems.

Crazy lace agate is a natural variety of agate (banded chalcedony, SiO₂) whose bands twist and turn in many colours. The classic material comes from the Sierra Santa Lucia in Chihuahua, Mexico, where it occurs mainly as vein agate in limestone. It is a natural stone; like other agate, beads in unusually bright colours may be dyed.

Dragon blood jasper (also sold as dragon stone or dragon's blood stone) is a trade name for natural green rock with red markings, and it is applied to more than one material. The Western Australian material, recorded by Mindat from the Geological Survey of Western Australia, is a chrome-rich fuchsite chert: microcrystalline quartz colored mid-green by minor fuchsite, sometimes with fine red iron-rich bands and blebs. The same names are also used for an epidote–piemontite rock (epidosite) marketed from South Africa.

A dzi (Tibetan gzi; Chinese tianzhu, "heavenly bead") is a bead of natural agate or chalcedony whose black-and-white pattern, typically eyes and stripes, was made by people by staining and etching the stone. Ancient dzi have been excavated from tombs about 2,000 years old in Tibet and Xinjiang. Most dzi on today's market are modern beads made in the same style, and imitations of glass, plastic, resin or metal also exist.

Emerald is the green to bluish green variety of beryl, a natural mineral species that also includes aquamarine and beryls of other colours. Its colour is caused by trace amounts of chromium or vanadium. Gemologists call paler stones green beryl rather than emerald, although opinions differ on where the boundary lies.

Eudialyte is a natural sodium-calcium zirconium silicate mineral of the trigonal eudialyte group, usually pink to deep red or brownish red. It forms in nepheline syenites and related pegmatites, and most gem material is massive rock from the Kola Peninsula, Russia, cut into cabochons, beads, spheres and carvings, often with black aegirine and white feldspar in the matrix. Transparent facetable crystals are rare and small.

Fluorite, also called fluorspar, is the calcium fluoride mineral CaF₂, a halide. It occurs in a very wide range of colors, including purple, green, blue, yellow, pink and colorless, and crystals are often color zoned. It defines hardness 4 on the Mohs scale.

Fossil coral, as used for beads and cabochons, is ancient coral whose original calcium carbonate skeleton has been replaced or filled by silica (chalcedony, opal and quartz) over millions of years. It is therefore a natural fossil made of silica minerals, not living-coral organic material. Geologists call it silicified coral when the coral's internal structure is preserved, and agatized coral when banded chalcedony (agate) fills the space the coral left.

Freshwater pearls on today's market are cultured pearls grown in freshwater mussels in lakes and ponds, mainly Hyriopsis cumingii (and hybrids) in China, the leading source. They are an organic gem made of nacre, not a mineral, and are the most commonly produced and most affordable pearl type, valued for their wide range of sizes, shapes and colours.

Garden quartz (also sold as lodolite) is a descriptive trade name for natural quartz (SiO₂) whose inclusions of other minerals, most often green chlorite, look like a garden or landscape inside the stone. It is not a separate mineral or a formally defined variety: the host is ordinary crystalline quartz, and what is included varies from piece to piece.

Grandidierite is a rare natural magnesium-aluminium borosilicate mineral, (Mg,Fe)Al3(BO3)(SiO4)O2, with a bluish green to greenish blue color that deepens with iron content. It was described in 1902 from southern Madagascar. Most material is translucent to opaque and cut as cabochons or beads; transparent faceted stones are very rare.

Gray moonstone is a color name for natural moonstone feldspar with a gray body color, showing the soft moving sheen called adularescence. GIA notes that moonstone can be gray to nearly black and pictures a gray moonstone from India. It is a trade color name, not a separate mineral, and the sources read do not state which feldspar species such material is.

Green aventurine is the green colour variety of aventurine, a natural quartzite or quartz rock, not a single mineral. Its colour comes from small flat inclusions of fuchsite, a green chromium-rich mica, which can also make the stone glitter (aventurescence). Green is the most common colour of aventurine. Despite the trade name "Indian jade" it is not jade, and it is neither goldstone (a man-made glass) nor sunstone (a feldspar).

Green calcite is a descriptive name for natural calcite (calcium carbonate, CaCO₃) with a green colour; it is a colour variety, not a separate mineral species. A translucent green calcite from Pakistan examined by a gem laboratory contained trace copper and manganese, but the sources consulted do not establish the cause of the green colour. Some green calcite is artificially dyed: Mindat records "Mexican Jade" as dyed green calcite.

Green fluorite is the green color variety of fluorite, the natural calcium fluoride mineral CaF₂. Green is one of fluorite's most typical colors, ranging from pale to deep and bluish green. Pure fluorite is colorless; studies attribute green to color centers linked to trace samarium (Sm²⁺) and to yttrium–cerium-associated centers. Fluorite has been offered as emerald, but it is a much softer, different mineral.

Green garnet is a color-based trade name for natural garnet, not a single mineral species. GIA names tsavorite and demantoid as green garnets: tsavorite is a green, chromium- and vanadium-bearing variety of grossular, and demantoid is the green to yellowish green variety of andradite. Other green grossulars, such as light "mint" garnet from Merelani, Tanzania, are also sold, while green uvarovite usually forms crystals too small to cut. A stone or bead sold as green garnet may therefore be any of these unless tested.

Green quartzite is quartzite, a natural metamorphic rock made almost entirely of interlocking quartz grains, that is green. Natural green colour comes from inclusions of fuchsite, a chromium-rich mica; when the mica flakes make the stone glitter it is sold as green aventurine, and much lapidary "aventurine" is in fact quartzite with little or no aventurescence. Quartzite is also dyed green to imitate jade, so a green quartzite bead may be natural or dyed.

Green tourmaline is a natural mineral: the green color range of tourmaline, a group of closely related borosilicate mineral species. Its trade name verdelite is described by Mindat as a green variety of tourmaline, most commonly elbaite or fluor-elbaite, with various other species possible. IGS reserves verdelite for green stones not colored by chromium or vanadium; intense green stones colored by those elements are sold as chrome tourmaline.

Hematite is an iron oxide mineral (Fe₂O₃) and the most important iron ore. Crystals are steel-grey to black with a metallic lustre, while earthy material is rust-red. Much of the "hematite" sold for jewelry is an artificially made material rather than the natural mineral.

Hidaka jade is a natural green rock from Chisaka in Hidaka Town, Hokkaido, made mainly of chromian diopside (diopside containing about 1% chromium). Despite its name it is neither jadeite nor nephrite; it was named for its jade-like interlaced texture, toughness and translucent green color and is sometimes called the "third jade". Found in 1966, the deposit was worked out within about three years.

Iolite is the trade name for gem-quality, violet-blue cordierite, a natural magnesium-aluminium silicate mineral (Mg₂Al₄Si₅O₁₈) named after the French geologist Pierre Louis Antoine Cordier. It is known for strong pleochroism: turned in different directions, one stone can look violet-blue, pale blue-gray or almost colorless to yellow. Other recorded names include dichroite and the misleading "water sapphire"; iolite is not a sapphire.

K2 granite is a natural rock from the Karakoram of northern Pakistan: a fine-grained white to grey granitic rock with blue spots of azurite, a copper carbonate mineral, and sometimes small green malachite stains. It is sold as "K2 granite", "K2 stone", "K2 blue" and "raindrop azurite"; the common trade name "K2 jasper" is misleading, because the rock is not jasper. GIA confirmed by Raman analysis that the blue spots are azurite in a matrix of sodic plagioclase, quartz and muscovite.

Kunzite is the light pink to violetish purple variety of the natural mineral spodumene, a lithium aluminium silicate (LiAlSi2O6). Other spodumene varieties are green hiddenite and yellow triphane. It was named after the gemologist George Frederick Kunz and often occurs as large, relatively clean crystals.

Kurama stone (Kurama-ishi) is a natural igneous rock from the Kurama area of Sakyo Ward, Kyoto: a Cretaceous quartz diorite whose main facies is hornblende–biotite tonalite, rich in the iron sulfide pyrrhotite. As the pyrrhotite oxidizes, the stone takes on a characteristic rust-brown color, and it has long been prized as a high-grade garden stone for tea gardens. Although sometimes sold as granite, it is a quartz diorite (a granitoid rock), not granite in the strict sense.

Kyanite is an aluminum silicate mineral (Al₂SiO₅) that forms during the regional metamorphism of clay-rich sediments. It shares its chemistry with andalusite and sillimanite (polymorphs). It is most often blue and grows as elongated blades whose hardness varies with direction. Synonyms include cyanite and disthene (also spelled distene). It is a raw material for refractory porcelain, and clear, deep blue material is cut as a gemstone.

Labradorite is a plagioclase feldspar, an intermediate member of the albite–anorthite series with an albite : anorthite ratio of about 30 : 70 to 50 : 50. Its body color is usually gray, brown or black, and many pieces show labradorescence, a play of blue, green, gold or other colors seen from certain angles. It is a common mineral in rocks such as gabbro, basalt and anorthosite, and is named after Labrador, Canada.

Larimar is the trade name for natural blue, massive pectolite, NaCa₂Si₃O₈(OH), from the Dominican Republic. Its white to sky-blue and deep-blue patterns are caused by traces of copper. Pectolite itself occurs worldwide, but this blue compact variety is known as a jewelry stone only from the Dominican Republic.

Lava stone is a natural volcanic rock, not a single mineral. The porous rock known as "lava rock" corresponds to scoria or vesicular basalt: dark lava that solidified while full of gas bubbles, leaving many small cavities (vesicles). Its composition is usually similar to basalt, a rock made mainly of plagioclase and pyroxene.

Lavender amethyst is a trade name for amethyst, the purple variety of quartz (SiO₂), in a soft, pale lavender tone. The Japanese retailer Pascle uses the name for pale lilac to lavender amethyst (a trade claim). A 2024 study from the China University of Geosciences (Wuhan) describes a new type of amethyst sold as lavender amethyst whose main distinguishing feature is a milky texture, and found that the existing material had been heat-treated.

Lemon chrysoprase (also citron chrysoprase) is a misleading trade name: the material is not chrysoprase or any chalcedony but a natural, opaque, pale yellow to lime-green rock composed mainly of nickel-bearing magnesite (magnesium carbonate), often with quartz. Its green color is attributed to nickel, probably as gaspeite (nickel carbonate) in solid solution with the magnesite. Geologists suggest "lemon magnesite" or "citron magnesite" as more accurate names.

Lemon quartz is a trade name for light yellow to yellow-green quartz (SiO₂). The material sold under this name is natural quartz whose colour has been produced by treatment: low-dose gamma irradiation followed by heating. In Brazil it is traded as Ouro Verde (Portuguese for "green gold"). Mindat lists "lemon quartz" as a synonym of citrine, but gemmological studies separate it from citrine by its colour cause and optical behaviour.

Libyan Desert Glass is a pale yellow to yellow-green natural glass of almost pure silica (about 98% SiO₂), found in the Great Sand Sea of western Egypt near the Libyan border. It formed about 28.5–29 million years ago from melted quartz-rich sand; recent studies point to a meteorite impact, though an airburst origin has also been argued and no source crater has been identified. It is an impact glass, often grouped with tektites, and is not a mineral or a meteorite.

Mahogany obsidian is natural obsidian, a volcanic glass, in which reddish-brown and black glass are swirled or banded together. The reddish-brown color is due to iron impurities, generally tiny crystals or inclusions of iron oxides such as hematite or limonite. It is untreated natural rock, not a mineral and not man-made.

Milky quartz is a natural variety of crystalline quartz (SiO₂) that is white and translucent to almost opaque. The white colour is not a pigment: it comes from countless evenly distributed tiny gas and/or fluid inclusions that scatter light. It is also called milk quartz or snow quartz, and the term is sometimes used for white, massive vein quartz.

Moldavite is a green natural glass, a tektite formed about 14.7 to 15 million years ago when an impact created the Ries crater in southern Germany and splashed molten surface rock mainly onto what is now the Czech Republic. It is not a mineral and not a meteorite, although the Chinese trade name 捷克隕石 ("Czech meteorite") suggests otherwise. Undisclosed man-made glass imitations are common in the market.

Moonstone is a variety of the feldspar-group mineral orthoclase. As it forms, orthoclase and albite separate into thin alternating layers; light scattered between these layers produces adularescence, a soft glow that seems to billow across the stone. Hecatolite is a recorded synonym.

Morganite is the pink to orange-pink variety of beryl, the natural mineral species that also includes emerald and aquamarine. Its colour is caused by traces of manganese, and it is usually light in tone. Untreated morganite often has an orange component that gives a salmon or peach colour; much of it is heated to make it pinker.

Moss agate is a natural variety of chalcedony (microcrystalline quartz, SiO₂): a colorless to white, translucent stone containing green, moss-like inclusions of minerals such as chlorite or hornblende, sometimes with brown to black dendrites of iron or manganese oxides. Despite the name it is usually not banded like a true agate. Mindat lists tree agate and medfordite as synonyms; "mocha stone" is an older name used inconsistently by vendors.

Mother-of-pearl, or nacre, is an organic gem material, not a mineral: the hard, iridescent inner layer of some mollusk shells, such as pearl oysters, mussels, abalone and some snails. It is mostly aragonite (calcium carbonate) held together by the protein conchiolin, the same material that makes up nacreous pearls. Mother-of-pearl is often used in its natural colors but is also frequently dyed.

Muscovite is a natural potassium-aluminium mica, KAl₂(AlSi₃O₁₀)(OH)₂, and the most common member of the mica group. Pure thin sheets are colorless to silvery white, but impurities tint it; Mindat notes that pink to red muscovite can owe its color to manganese (Mn³⁺) rather than lithium. The dark pink to red-brown beads sold as "muscovite" in the crystal trade are described by the Japanese retailer Pascle as manganese-colored muscovite, which is consistent with this, although no laboratory test of those beads was found.

Nuummite is a natural metamorphic rock from the Nuuk region of West Greenland, made almost entirely of orthoamphiboles of the anthophyllite–gedrite series. Its grains consist of alternating submicroscopic lamellae of anthophyllite and gedrite, which produce iridescence in gold, blue, green and other colors on a gray to black ground when the stone is cut. Nuummite is a trade name, not an approved mineral name; it means "from Nuuk" in Greenlandic.

Orange aventurine is an orange colour variety of aventurine, a natural quartzite or quartz rock whose small platy inclusions can make it glitter (aventurescence); the iron oxides hematite and goethite produce orange to red and brown tones. The Japanese retailer Pascle says its orange aventurine shows little aventurescence and is sometimes called orange quartzite. It is a natural rock, not goldstone glass and not sunstone feldspar.

Orange moonstone is a color name for natural moonstone feldspar with a light orange to orange body color, showing the soft moving sheen called adularescence. GIA pictures light orange and orange moonstones from India among the many colors moonstone can have. It is a trade color name, not a separate mineral, and the sources read do not state which feldspar species such material is.

Peridot is gem-quality olivine, typically yellowish green.

Petrified wood is a plant fossil, not wood and not a single mineral species: it is ancient wood whose pores were filled and whose tissue was partly or wholly replaced by silica, so that it is now made mostly of quartz while keeping the shape and often the cell structure of the tree. Paleontologists describe the processes as permineralization and replacement; silicification (by silica) is the most common type in fossil wood.

Phosphosiderite is a natural hydrated iron phosphate mineral (FePO₄·2H₂O) of the metavariscite group, typically purple to reddish violet or rose-red. It is the monoclinic dimorph of strengite and usually forms as an alteration product of primary phosphates in granite pegmatites. Massive purple material is cut into cabochons and beads, and gem laboratories have found such material impregnated with polymer or epoxy resin.

Pink aventurine is a pink to reddish-brown colour variety of aventurine, a natural quartzite or quartz rock whose small platy inclusions can make it glitter (aventurescence). Its pink tones come from flakes of lepidolite mica or from the iron oxides hematite and goethite. The Japanese retailer Pascle describes the stone it sells under this name as pink to brownish red. It is a natural rock, not goldstone glass and not sunstone feldspar.

Pink calcite is a descriptive name for natural calcite (calcium carbonate, CaCO₃) with a pink colour; it is a colour variety, not a separate mineral species. In studied samples the pink colour is linked mainly to manganese replacing calcium (manganese-bearing, or manganoan, calcite). Cobalt-bearing calcite, which ranges from pink to purplish red, is another type.

Pink chalcedony is chalcedony, the microcrystalline form of quartz (SiO₂), in a pale pink color. Natural pink chalcedony exists, but because chalcedony is porous and easily dyed, pink chalcedony on the market may be natural or dyed. In the gem trade the plain name "chalcedony" is used for translucent stones of a single color, including pink.

Pink coral is an organic gem: the polished calcium carbonate skeleton of a colony of tiny marine animals (polyps), not a mineral. Untreated pink coral of jewellery quality is precious coral from the family Coralliidae, chiefly Pleurocorallium elatius (trade names momo, cerasuolo, satsuma; its light pink form is called angel's skin) and Pleurocorallium secundum (Midway, rosato). Much inexpensive pink coral in the bead trade is instead dyed: CIBJO notes that common bamboo coral is commonly bleached and dyed pink to imitate precious coral, so a dyed bead's species cannot be assumed.

Pink opal is a natural, opaque to translucent pink common opal: it shows no play-of-color. The best-known material comes from the Acari area of Arequipa, Peru, where studies found that most pink samples are opal-CT containing the fibrous clay mineral palygorskite, which is linked to the pink color. Similar palygorskite-bearing pink opal is also known from Mexico.

Pink tourmaline is the pink color variety of tourmaline, a group of boron silicate minerals; most gem tourmalines, including pink ones, are elbaite (liddicoatite also occurs). Its pink to red color is generally attributed to manganese, though some pink elbaites may owe their hue to color centers caused by natural or laboratory radiation. Deeper pink to red stones are sold as rubellite, although some in the trade argue that rubellite should not include pink tourmaline.

Prasiolite is a green, transparent variety of quartz (SiO₂). Most prasiolite on the market is produced artificially, by heating amethyst or by irradiating and heating quartz; natural occurrences are rare. It is often sold as "green amethyst", but Mindat calls that a highly confusing and officially discouraged trade name: the stone is green quartz, not amethyst.

Queen conch shell is an organic gem material, not a mineral: the shell of the queen conch (Aliger gigas, formerly Strombus gigas or Lobatus gigas), a large Caribbean sea snail. Its pink, cream and white shell is made of aragonite with a porcelain-like, non-nacreous luster and a silky "flame" structure; it is not mother-of-pearl. The species is listed in CITES Appendix II, so international trade in it, including its shell, is regulated under CITES.

Rainbow fluorite is a trade name for natural fluorite (calcium fluoride, CaF₂) that shows two or more colors in one piece. The International Gem Society notes that lapidaries cut such multicolored gems from color-zoned crystals; fluorite crystals are frequently color zoned. Pascle, a Japanese retailer, uses the name for beads with several colors in one bead, most often green and purple, and notes it is also sold as "bicolor fluorite". It is the same mineral as other fluorite, not a separate species.

Red coral is an organic gem: the polished calcium carbonate skeleton of a colony of tiny marine animals (polyps), not a mineral. Untreated red coral of jewellery quality is precious coral from the family Coralliidae, such as Mediterranean Corallium rubrum and Japanese Corallium japonicum (trade names aka, moro, oxblood). Much inexpensive red coral in the bead trade is instead dyed: CIBJO notes that common bamboo coral is commonly bleached and dyed red to imitate precious coral, so a dyed bead's species cannot be assumed.

Rhodochrosite is a natural manganese carbonate mineral (MnCO3) of the calcite group, pink to rose-red in color. "Inca Rose" is a trade name for the same mineral. Banded massive material is cut into beads, cabochons and carvings; rare transparent crystals are faceted for collectors.

Rhodolite is a natural purplish red garnet whose composition lies in the pyrope–almandine series. Mindat notes that the name originally meant a rose-red gem variety of pyrope but now covers pink to purplish garnets in that series, many of them closer to almandine. IGS stresses that the purplish red hue, not an exact recipe, defines rhodolite, and that small amounts of other garnet species are always present.

Rhodonite is a natural manganese silicate mineral (rhodonite group, triclinic) with a pink to rose-red color, often veined with black manganese oxides. Massive, opaque material is widely carved into beads, cabochons and objects, while transparent faceted stones are rare because of the mineral's perfect cleavage.

Rock crystal is the traditional name for clear, colourless quartz (silicon dioxide, SiO₂), a natural mineral. It is one variety of quartz, not a name for the whole quartz family: coloured varieties such as amethyst, citrine and rose quartz have their own names. Except for being colourless and clear, it has no property that other crystalline quartz lacks.

Ruby in zoisite, also called anyolite, is a natural metamorphic rock rather than a single mineral: bright green chromium-bearing zoisite containing opaque purplish-red to pink ruby (corundum) crystals, often with black to very dark green amphibole (pargasite, also described as hornblende or tschermakite). It was first reported in 1954 near Longido, Tanzania, and is cut into cabochons, beads, carvings and small sculptures.

Sajigawa stone (Sajigawa-ishi) is a natural metamorphic rock from the Saji area of Tottori City, Tottori Prefecture: a dark, blackish-green rock derived from basaltic lava and pyroclastic rock of Paleozoic submarine volcanoes, belonging to the Sangun metamorphic belt. It is counted among Japan's three famous stones and is prized as a bonseki, garden stone and suiseki; collection has been prohibited since 1965.

Santa Maria aquamarine is a trade name for aquamarine (blue beryl, a natural mineral) of a rare, medium-dark, highly saturated blue. The name comes from the Santa Maria de Itabira mine in Minas Gerais, Brazil, which is now nearly exhausted; today the trade uses it mainly for a colour rather than a locality, including stones from African deposits. It is not a separate mineral species.

Sardonyx is a natural banded chalcedony (cryptocrystalline quartz, SiO₂), classed by Mindat as a variety of agate, in which brownish red to orange layers of sard alternate with white or black layers of onyx. It is one of the three August birthstones and, according to GIA, the original one. Mindat lists "carnelian onyx" as a synonym.

Sea Blue Chalcedony is a trade name for natural chalcedony (microcrystalline quartz, SiO₂) that has been dyed a vivid light blue; the color is not natural. It was introduced at the Tucson gem shows in February 2002 by the supplier Maxam Magnata of Tucson, Arizona, as color-enhanced chalcedony, later described by the company as a dyed translucent material sold as Sea Blue Chalcedony™.

Selenite is the transparent, crystalline variety of gypsum, a natural hydrous calcium sulfate mineral (CaSO₄·2H₂O); it contains no selenium. Mindat notes that the name is mostly synonymous with gypsum and has historically meant the transparent variety, as opposed to fibrous satin spar and fine-grained alabaster. White, silky material showing a cat's-eye band, such as the beads the Japanese retailer Pascle sells as selenite, matches the definition of satin spar gypsum rather than transparent selenite.

Seraphinite is a trade name for a natural, dense, fine-grained variety of clinochlore, a soft magnesium-aluminium silicate of the chlorite group, whose radiating, feather-like (plumose) structure gives a silvery shimmer on a dark green to grey ground. It is used for carving and as a decorative stone. Mindat records it from the Korshunovskoye iron deposit in Irkutsk Oblast, Siberia, Russia.

"Shell pearl" is a man-made imitation pearl, not a natural or cultured pearl: a bead cut from mollusk shell is coated with an artificial pearly layer to look like a pearl. GIA considers the name misleading; under CIBJO rules such products must be called "imitation" or "simulated" pearls.

Shungite is a natural, black, carbon-rich material from Karelia in north-western Russia. It is not a crystalline mineral but a mineraloid: original shungite is non-crystalline carbon with about 98 wt% C, while the same name is also used for shungite rocks, metamorphosed ancient oil shales that contain far less carbon. Mindat treats lustrous shungite as a variety of pyrobitumen.

Silver obsidian is natural obsidian, a volcanic glass, that shows a silvery sheen; it is a form of sheen obsidian. The sheen is caused by light reflecting from minute inclusions such as tiny flattened gas bubbles or needle-like inclusions. It is untreated natural material, not a mineral and not man-made.

Soapstone, also called steatite, is a natural metamorphic rock made mostly of the soft mineral talc, with varying amounts of chlorite, micas, amphiboles, pyroxenes and carbonates. It is named for its soapy feel and softness, and is usually gray, bluish, green or brown. The pink beads sold in Japan as "soapstone" or "pink talc" were reported by the retailer Pascle, citing a Japanese gem laboratory, to be natural talc with a wax-coated surface; the sources read here do not explain their pink color. The word "soapstone" is also used loosely in the craft trade for other soft rocks such as alabaster or serpentine.

Stichtite is a natural, very soft, rose-pink to purple mineral, a hydrated magnesium-chromium carbonate-hydroxide of the hydrotalcite group, named after Robert Carl Sticht of the Mount Lyell Mining and Railway Company in Tasmania. It forms in altered serpentinites with chromite, and is often found mixed with green serpentine.

Sugilite is a natural mineral, a potassium-sodium-iron-lithium silicate of the osumilite group, first described as a new species from Iwagi Islet, Ehime Prefecture, Japan, and named after the Japanese petrologist Ken-ichi Sugi. The original Japanese material was yellowish and of no gem value; the opaque to translucent purple gem material, coloured by manganese, comes mainly from the Wessels Mine area in South Africa's Kalahari manganese field.

Super Seven (also sold as Sacred Seven or Melody Stone) is a trade name, not a mineral name, for natural quartz, mostly amethyst and smoky quartz, that contains inclusions of other minerals. Sellers claim it holds seven minerals: amethyst, clear quartz, smoky quartz, rutile, goethite, lepidocrocite and cacoxenite. Three of these are colour varieties of quartz itself, and Mindat managers report that pieces on sale never showed all seven and that the "cacoxenite" and "lepidocrocite" were often really goethite and hematite.

Tanzanite is the transparent violet-blue to blue-violet variety of the natural mineral zoisite, a calcium aluminium silicate. It is mined commercially only in the Merelani Hills of northern Tanzania, after which Tiffany & Co. named it. Most tanzanite on the market has been heat treated to remove brownish or yellow-green tones and bring out its blue and violet colour.

Tektites are natural glasses, not minerals and not meteorites: they are Earth rocks or sediments melted by a large meteorite impact, thrown through the atmosphere and quenched into glass. Most are black, though moldavites are green; they are rich in silica, contain almost no water and occur over wide areas called strewn fields. The Chinese name 玻璃隕石 ("glass meteorite") is traditional but misleading.

"Terahertz" or "terahertz stone" is a trade name for a man-made material, not a natural stone or mineral. A 2022 gemmological study by Chinese testing laboratories, published in China Gems, found that the beads sold under this name consist mainly of monocrystalline silicon, the same kind of material used for semiconductors and solar cells. "Terahertz" (THz) is simply a unit of frequency; the name does not describe a mineral.

Unakite is a natural rock, not a single mineral: an altered granite made chiefly of pink orthoclase feldspar, green epidote and white to smoky quartz. The epidote formed secondarily, replacing the mica or hornblende of the original granitic rock. It takes a high polish and is used as an ornamental stone.

Variscite is a natural hydrated aluminium phosphate mineral (AlPO₄·2H₂O), usually yellowish green to bluish green and found as fine-grained nodules, veins and crusts. Gem material is cut into cabochons, beads and carvings and can closely resemble turquoise. It forms a series with the iron-dominant mineral strengite.

Vesuvianite is a natural silicate mineral, a calcium-aluminium sorosilicate with variable magnesium and iron, recognised by the IMA as a valid species. It is also widely known as idocrase, an older name that is still common in the gem trade. Transparent crystals are faceted as collector gems, while compact green material is cut into beads and cabochons or used as a jade substitute.

White chalcedony is natural chalcedony, the microcrystalline form of quartz (SiO₂), in a white to off-white color. Pure chalcedony is white, gray or bluish; other colors come from included minerals. In the gem trade the plain name "chalcedony" is used for translucent stones of a single color, and white is one of the colors sold this way.

White labradorite is a trade name for natural labradorite, a plagioclase feldspar, with a colorless to white, often transparent to translucent body and a multicolored sheen. The same material is widely sold as "rainbow moonstone"; GIA explains that this is labradorite, not orthoclase moonstone, although the trade accepts the name. Much of it comes from Madagascar.

Yamanashi crystal is natural quartz (SiO₂) mined in Yamanashi Prefecture, Japan, mainly in the granite mountains around Mount Kinpu (Kinpusan). It is a locality name, not a separate mineral: the deposits yielded colourless rock crystal as well as white, smoky, chlorite-included and, rarely, amethyst quartz. Mining flourished in the Meiji era and has since ended; the largest mine, Otome, closed in 1981.

Yellow tourmaline is a natural mineral: the yellow color range of tourmaline, a group of closely related borosilicate mineral species. The name does not fix one species. According to Gems & Gemology, the most important source of yellow gem elbaite is the Canary mining area in eastern Zambia, whose manganese-rich stones have been marketed as Canary tourmaline since 2001, while GIA notes that bright yellow "savannah" tourmalines are dravite–uvite mixtures colored by iron.

Zeolite is not a single mineral but the name of a large group of natural minerals: hydrated framework aluminosilicates of alkali and alkaline-earth metals whose structure contains open channels and cages holding water and exchangeable cations. About 40 natural zeolites are known, and many more have been synthesised for industry. Material sold simply as "zeolite" (usually white) does not, by that name alone, tell which zeolite species it is.