Willemite
Willemite is a silicate mineral prized by collectors for its exceptional color range, with known Chinese sources.
Willemite is a zinc silicate famous as one of the brilliantly fluorescent minerals of Franklin, New Jersey, where it glows vivid green under ultraviolet light.
About Willemiteextended article
Willemite (Zn₂SiO₄) is a zinc silicate, a minor ore of zinc and a celebrated collector species — above all for its intense green fluorescence under ultraviolet light.
The Franklin connection
The Franklin and Sterling Hill zinc deposit in New Jersey is the classic willemite locality, where it occurs with franklinite and calcite and fluoresces brilliant green (the calcite glows red) — the defining display of fluorescent mineralogy.
What collectors look for
Fluorescent willemite–franklinite–calcite assemblages are the signature; well-crystallised willemite and a strong UV response drive value.
About Willemite
Willemite is classified as a silicate mineral in the phenakite group and has the chemical formula Zn2SiO4. It crystallizes in the trigonal 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 short hexagonal prismatic crystals; also massive, granular, fibrous. Its color range is broad, including colorless, white, gray, pale green, yellow, and brown. The luster is vitreous, resinous, the streak is white, and specimens range from transparent to opaque. The cleavage is good {0001} and {1120}. The fracture is uneven to subconchoidal, which aids identification.
Collector context
How it forms
In terms of geology, Willemite forms in franklin-type metamorphosed zn-mn ore bodies; also in zn-bearing skarns and oxidized zn deposits; secondary mineral in some gossans. It is commonly found in association with franklinite, zincite, calcite, rhodonite, tephroite, sphalerite.
Classic Chinese localities
Willemite is widely represented across Chinese provinces, including Hunan, Yunnan, Sichuan, Henan.
Why collectors care
Willemite is a frequently-sought species in serious collections because its habit is recognizable, its color often strong, and its best examples unmistakable even at a distance. Chinese material has driven much of the recent visual shift in the species — sharper crystals, deeper colors, cleaner matrix.
What affects value
Value in Willemite 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 Willemite 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.