Wulfenite

Common mineral of the sulfate class.

Wulfenit Wulfenite Tsumeb Namibia
Large (5.13cts) wulfenite from Tsumeb, Namibia

As common as wulfenite may be (mindat lists more than 2000 localities on all continents except Antarctica), facetted gems are extremely rare and quite expensive. Wulfenite crystals normally are much too thin for cutting. Moreover the mineral is very soft, well cleavable, heat sensitive and rather brittle.
 

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Origin of name: in 1772 Austrian Mineralogist Ignaz Edler von Born, named the mineral "Plumbum spatosum flavo-rubrum, ex Annaberg, Austria".
In 1845 Wilhelm Karl von Haidinger, another Austrian Mineralogist and Geologist, renamed the ore wulfenite in honour of Franz Xaver Baron of Wulfens, who had discovered it and published a treaty about Carinthian leadspars.

Synonyms and trade names: Carinthite, lead molybdate, yellow lead ore, yellow leadspar

Can be confused with: due to the extremely high specific gravity wulfenite can only be confused with other very dense minerals like cassiterite, scheelite, cerussite or stibiotantalite

Localities: very common, type locality is Bad Bleiberg in Carinthia, Austria

Handling: because of the low hardness, its cleavability, its sensitivity to heat and its brittleness wulfenite is unsuitable for jewellery use.

Worth knowing: Franz Xaver Baron of Wulfen was (amongst many other things) also a botanist who discovered several new plants, amongst them Wulfenia carinthiaca a rare blue flower, endemic to an area of only about 10km² on the Austrian-Italian border.
 

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Gemmological Properties of Wulfenite

Formula:
Pb[MoO4]
Crystal system:
tetragonal
Mohs hardness:
2.5-3
Specific gravity:
6.5-7.5
Refractive index:
2.283-2.405
Max. Birefringence:
0.122
Pleochroism:
weak
Lustre:
resinous to adamantine
Cleavage:
distinct
Fracture:
irregular/uneven, sub-conchoidal, very brittle
Colour:
yellow, orange to red, reddish brown to black, rarely green (Mexico) and colourless