Willemite

Willemite is a zinc silicate mineral and minor ore of zinc.

It is probably best known by fluorescent mineral collectors, particularly from the Sterling Mine, New Jersey, USA. Fine specimens are found from the Tsumeb Mine of Namibia, too.

Information about Willemite

Willemite typically forms as crystals (often prismatic, stout or slender, terminated by rhombohedral faces) or massive, granular aggregates.

The minerals colour in daylight varies widely: colourless, white, yellow, greens (from pale to apple-green), brown, red-brown, and even blue or grey in some cases.

It is transparent to translucent in small, gemmy pieces; more often translucent to opaque in bulk specimens. Under short-wave UV light it sometimes fluoresces a brilliant green; under long-wave UV it may show yellow-green to weaker green fluorescence.

 

Uses and History

It is typically used as a minor ore of zinc, but I suspect most people reading this page are fluorescent mineral collectors, and that is where willemites true value lies, as a gorgeous fluorescent mineral.

Willemite was first described in 1830, named by Armand Lévy in honour of William I of the Netherlands. Its type locality is Vieille-Montagne (Belgium).

It is well known from several classic zinc ore localities, perhaps most famously Franklin and Sterling Hill in New Jersey, which also produced spectacular fluorescent specimens.

 

Mineralogy

Chemistry
A zinc silicate mineral with the formula Zn2SiO4.
Colours and Variations

Colourless, white, grey, red, brown, brown-red, honey, green, blue.

Streak
White
Luster
Vitreous to resinous.
Transparency
Transparent to opaque.
Fracture
Transparent to opaque.
Crystal habit
Prismatic crystals, can also be fibrous, botryoidal, massive.
Mohs hardness
5.5
Fluorescence
Typically a bright fluorescence under SW and LW light, glows yellow, orange or green.
Specific Gravity
3.89-4.19
Easiest testing method

Hazards and Warnings

Mineral collectors should wash their hands after handling specimens, to avoid any exposure to potential toxins.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

 

Translations

Arabic:

  • فيليميت

Hindi:

Portuguese:

Bengali:

Indonesian:

Punjabi:

English:

  • Willemite

Italian:

Russian:

  • Виллемит

French:

Japanese:

Spanish:

  • Willemit

German:

  • Willemit

Korean:

Thai:

Gujurati:

Mandarin Chinese:

  • 硅锌矿

Urdu:

Further Reading / External Links