Aug 21, 2014

A to Z of Gemstones - W is for Willemite

Willemite is a zinc silicate mineral and a minor ore of zinc.It was named after King Willem (William) the first (1772-1843) of The Netherlands, by the French mineralogist Armand Lévy whom discovered it in 1830 on former Dutch soil (present day Belgium). 

Willemite is usually colorless or white but can be tinted yellow, blue, red, brown and often green. A canary-yellow variety of willemite from Tsumeb, Namibia has also been documented.

The willemite from Franklin and Ogdensburg, Sussex County, New Jersey commonly fluoresces a brilliant green under Short Wave ultraviolet. This fluorescence combined with the red fluorescence of the calcite at Franklin, makes specimens from there even more special. Some willemite specimens will even show phosphorescence. Phosphorescence is the ability of a mineral to glow after the initial light is removed.

Willemite occurs as a mineral in metamorphosed zinc ore deposits. It is uncommon, except at the zinc mines of Franklin and Ogdensburg in Sussex County, New Jersey. It has however also been found in Arizona, USA; Morsnet, Belgium; St. Hilaire, Quebec; Tsumeb, Namibia and Greenland. 

As a gemstone, faceted willemite is rare although it has been cut as an uncommon, exotic gem. Fine-quality gemstones have been cut from orange-yellow willemite crystals. Facet-grade willemite has also been recovered from the Tsumeb (Tsumcorp) Mine in Tsumeb, Namibia.

I have had trouble finding any examples of Willemite jewelry at all but eventually found a couple:

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