Click on a letter above to view the list of gems.    

Willemite
Current inventory:  3 gems
 

Chemistry:  Zn₂SiO₄  [Zinc Silicate]

Discovered in 1830;   IMA status: Valid (pre-IMA; Grandfathered).
Willemite is named in honour of William I (Willem), King of the Netherlands (1813-1840).

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/A.01-20

8 : Silicates
A : Nesosilicates, with [SiO4]4- groups, cations of tetrahedric orientation [4]
01 : Phenakite series

Crystal Data

Crystallography:

Trigonal - Rhombohedral

Crystal Habit:

Crystals prismatic, both stout and slender, terminated by rhombohedra, to 10 cm. Coarse to fine granular, disseminated; in fibrous aggregates, botryoidal, and massive.

Physical Properties

Cleavage:

Indistinct

Fracture:

Irregular to conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5

Density:

3.89 - 4.19 (g/cm³)

Luminescence:

Strong Fluorescence; bright Green in both SW UV and LW UV.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Yellow, Green, Reddish brown, Black.

Transparency:

Transparent to Translucent to Opaque

Luster:

Vitreous to resinous

Refractive Index:

1.691 - 1.730  Uniaxial ( + )

Birefringence:

0.010 - 0.028

Dispersion:

Strong

Pleochroism:

Colorless

Occurances

Geological Setting:

Of secondary origin, especially in zinc deposits developed in limestones; while uncommon, locally an important ore of zinc.

Type Locality:

Vieille Montagne (Altenberg; Kelmisberg), Moresnet, Kelmis, Plombières-Vieille Montagne District, Verviers, Liège Province, Belgium

Year Discovered:

1830

View mineral photos:

Willemite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Willemite is a rare mineral known and desired by collectors for its wonderful fluorescence. Willemite specimens fluoresce a bright green under ultra-violet light. It is one of the best examples of a fluorescent mineral and is a must have for collectors. Willemite is a zinc ore and although rare, was once found in abundance at Franklin, New Jersey. It was found in association with Zincite there. Willemite is one of the few silicate minerals that have a trigonal crystal symmetry. This symmetry is much more common among carbonates than silicates. Willemite is usually found as colorless, white, gray, various shades of green, yellow, orange and red-brown crystals. Some Willemite specimens will even show phosphorescence. Phosphorescence is the ability of a mineral to glow after the initial light is removed. The mineral has stored the energy of the light and re-emits light for a short time.
 

  
Willemite gems for sale: