Willemite

Description

A strongly fluorescent mineral composed of Zinc silicate that has been used as a gemstone. Willemite was named after Willem I (1772-1843) king of the Netherlands. It is transparent or translucent in shades of yellow, green, red, brown, blue, black or white. Willemite occurs in the U.S. (New Jersey, New Mexico), Belgium, Zaire, Algeria, Namibia, and Greenland.

Synonyms and Related Terms

troostite; willemita (Esp.); willémite (Fr.); willemiet (Ned.)

Physical and Chemical Properties

• Hexagonal system with short prismatic or rhombohedral crystals; may be fibrous massive.
• Cleavage is good in three directions.
• Fracture = uneven to conchoidal.
• Luster = resinous to vitreous.
• Streak = white
• Strongly fluorescent

Composition	Zn2SiO4
Mohs Hardness	5.5
Density	3.9-4.2 g/ml
Refractive Index	1.70; 1.72

Resources and Citations

• Mineralogy Database: Willemite