Dendritic Quartz

Dendrites form where solutions carrying manganese or iron seep into narrow spaces and deposit oxides. The Tokushima Prefectural Museum explains that rainwater and groundwater entering joints in rock deposit manganese there, so dendrites appear only on such crack surfaces and never on fresh breaks; Mindat adds that dendrites can be flat deposits on a surface or in a fracture, or three-dimensional within a permeable material. The retailer Pascle lists Brazil, the USA and Madagascar among the sources of dendritic quartz.

Dendrites look like fossil ferns or leaves but are mineral deposits; Mindat notes that they are often mistaken for fossils. The Tokushima Prefectural Museum points out that plant fossils occur almost only in sedimentary rocks, whereas dendrites appear in many kinds of rock and only along joint surfaces. Caltech mineral spectroscopists report that the mineral making up a dendrite cannot be told from its appearance, and that although textbooks often call dendrites pyrolusite, they have found other manganese oxides instead. The host can be confirmed as quartz by its standard properties (hardness 7, refractive index 1.544 to 1.553).

IGS lists no special care instructions for quartz. The retailer Pascle notes that the dendrites are metal-bearing minerals that may be affected by moisture or salt, and advises care where they reach the surface of a bead.

In Japan, fern-like dendrite patterns on rocks are called shinobu-ishi (しのぶ石, 忍石), also jukei-seki (樹形石) or mojuseki (模樹石); according to the Tokushima Prefectural Museum, the name comes from the shinobu fern, long grown in Japan as an ornamental plant. The retailer Pascle notes that the word dendrite comes from the Greek dendron, "tree".

The retailer Pascle says that, because of its plant-like pattern, dendritic quartz is popular as a charm for relaxation, and that its tree-like branches are associated with patience and steady growth.