Billwiseite

Billwiseite is a very rare oxide mineral found at the pegmatite commonly referred to as "Stak Nala" located within a few hundred yards from the village of Toghla in the Stak Nala, Gilgit-Baltistan, Pakistan. It has only been found as a coating on a single crystal of lepidolite. The sole rock containing Billwiseite is kept at the Royal Ontario Museum, catalogue number M5595.^[3][4]

Billwiseite
General
Category	Oxide minerals
Formula	(Sb3+)5(Nb,Ta)3WO18
IMA symbol	Bwi[1]
Strunz classification	4.DX
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/c
Unit cell	a = 54.206(6) Å, b = 4.9163(5) Å, c = 5.5540(6) Å; β = 90.396(2)°; Z = 4
Identification
Color	Pale yellow (with a tinge of green)
Cleavage	{100} Indistinct
Fracture	Hackly
Mohs scale hardness	5
Luster	Vitreous
Streak	Colorless, very pale yellow
Specific gravity	6.33
Refractive index	unknown
References	[2][3][4]

It contains four relatively uncommon elements: antimony, niobium, tantalum, and tungsten. It is named after William Wise, a mineralogist from the University of California, Santa Barbara.^[4]

It was discovered by an international group of geologists, and accepted by the IMA in 2010. Its discovery was announced in Mineralogical Magazine in 2011, and was described in detail in 2012 in The Canadian Mineralogist by Hawthrone et al.^[4]