|After king William I of the Netherlands
|Colorless, white, gray, various shades of green, yellow, orange, red-brown
|5.5 on Mohs Scale
|Hexagonal. Crystals prismatic, short and stubby or long needles; massive compact; granular
|Poor. Fracture conchoidal. Brittle
|Specific Gravity (SG)
|3.89 - 4.10
|Vitreous to resinous
|Faceted gems are known to a maximum size of 10 carats, mostly from the Franklin, New Jersey, occurrence. Cabochons to several inches are frequently
cut from massive Franklin material.
|Intense green or yellow-green in SW, also in LW. Sometimes intensely phosphorescent (green)
Note: Cabochons of massive brown troostite from New Jersey are attractive, as are cabochons of willemite with black franklinite and red zincite in white calcite. Faceted willemite is extremely rare and stones larger that 1-2 carats are worthy of museums. Most such stones are pale green, yellow-orange, or brownish green, rarely blue. Gems are difficult to polish, and the material is too soft and fragile for use in jewelry.
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