Rainbow Fluorite

Fluorite forms mainly in hydrothermal veins, often with metallic ores, and in cavities of limestones and dolomites; it is common worldwide. Multicolored, color-zoned crystals occur at many fluorite localities. Pascle lists China and the USA as the main sources of the rainbow fluorite it sells.

Rainbow fluorite has the properties of fluorite: hardness 4, perfect cleavage in four directions, a very low refractive index (about 1.43) and specific gravity about 3.18; its color bands are part of the crystal, not a surface layer. Fluorescence is common but not diagnostic, since not all fluorite fluoresces. Color can be lightened by heating or deepened by irradiation, and decorative pieces may be coated, dyed or plastic-impregnated.

Like all fluorite, it is soft (Mohs 4) and cleaves easily, so ring wear is not recommended; pendants, earrings and protective settings suit occasional wear. Store it apart from harder gems and out of strong light, since some fluorite fades with prolonged light exposure. Fluorite is slightly soluble in water: do not soak it, clean it only with a warm damp cloth, mild detergent and a soft brush, and avoid mechanical cleaning systems.

Banded, multicolored fluorite has long been used decoratively. The International Gem Society notes that for over 1,500 years English artisans carved Blue John (Derbyshire Spar), a fluorite variety with bands of white, blue, violet and reddish brown, into vases, bowls and other objects; the Derbyshire deposits are nearly exhausted.

Pascle, a Japanese retailer, says fluorite is sometimes called the "stone of genius" because it is said to boost imagination, and that rainbow fluorite is said to combine the meanings attributed to each of its colors.