Zoisite
Zoisite is a silicate mineral prized by collectors for its exceptional color range, with known Chinese sources.
About Zoisite
Zoisite is a silicate mineral in the epidote group and has the chemical formula Ca2Al3(Si2O7)(SiO4)O(OH). It crystallizes in the orthorhombic system and is one of the most visually varied minerals in the collector market. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
Identification & care
Specimens usually show prismatic crystals with striated prism faces; also massive, granular. Its color range is broad, including gray, white, greenish-gray, yellowish (non-gem), blue-purple (tanzanite gem variety), pink-red (thulite — now separate), and green (chrome-bearing from tanzania). The luster is vitreous, pearly, the streak is white to colorless, and specimens range from transparent (gem) to translucent/opaque (massive). The cleavage is perfect {010}, imperfect {100}. The fracture is uneven to conchoidal, which aids identification.
Collector context
How it forms
The geological setting for Zoisite is typically medium-grade regional metamorphism of calcium-rich rocks; hydrothermal alteration; calc-silicate rocks (skarns); the gem varieties (tanzanite) form in graphitic gneisses under specific p-t conditions. It is commonly found in association with epidote, clinozoisite, hornblende, corundum (ruby), pyrite, calcite, phlogopite.
Classic Chinese localities
Zoisite is widely represented across Chinese provinces, including Gansu, Anhui, Guangdong, Guangxi.
Why collectors care
Collectors pursue Zoisite for the clarity of its crystal form and, in good material, saturated color that reads instantly across a display case. A well-terminated zoisite on clean matrix photographs well, identifies quickly, and anchors a cabinet piece. Top Chinese specimens over the last two decades have reset the bar for what zoisite looks like at collector grade.
What affects value
Value in Zoisite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.
Naming history
The name Zoisite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.