Queitite
General
Category	Minerals
Formula	Pb4Zn2(SO4)(SiO4)(Si2O7)
IMA symbol	Que
Strunz classification	9.BF.20
Dana classification	58.1.3.1
Crystal system	Monoclinic
Crystal class	Sphenoidal H-M Symbol: 2
Space group	P21
Unit cell	719.46
Identification
Color	Colorless, White, Pale Yellow
Twinning	{100} and {001}
Cleavage	Indistinct on {010} and {001}
Mohs scale hardness	4
Luster	Greasy
Streak	White
Diaphaneity	Transparent
Specific gravity	6.07
Density	6.07
Optical properties	Biaxial (+)
Refractive index	nα = 1.899(4) nβ = 1.901 nγ = 1.903(4)
Birefringence	0.004
2V angle	Measured: 90° Calculated: 88°
Dispersion	Extreme r < v
Major varieties
Calcian queitite	Ca4Zn2(SO4)(SiO4)(Si2O7)

Queitite is a lead zinc silicate sulphate that was named after the mineral dealer Clive S. Queit, who collected the first specimens. It got approved by the IMA in 1979,^[1] and it is an extremely rare secondary mineral.^[2]

When discovered at 1979 in Tsumeb, Namibia, Keller described the mineral occurring on a matrix, having euhedral bladed crystals - crystals with well defined smooth faces. Later on a cavity was discovered which contained queitite. The cavity's specimens were druzy and white, forming botryoidal crystals - crystals with a spherical habit. These crystals formed a 0.5 mm thick encrustation, and had a silky, fibrous structure.^[3] Queitite does not show any radioactive properties. It mainly consists of lead (62.98%) and oxygen (18.24%), but otherwise contains zinc (9.94%), silicon (6.40%) and sulfur (2.44%).^[4] Calcian queitite is the calcium bearing variant of queitite. Instead of lead, it contains calcium in its formula. This queitite variant was originally reported from the Lucky Cuss Mine, Arizona, USA. It was observed to be white and chalky, replacing the alamosite in the mine. It is described as having spheluritic modules.^[5]

It is a type locality of Tsumeb mine, Namibia, but it is also mined at Red Gill mine, England,^[6] and in the Penrhiw Mine, Ceredigion. However, there was one occurrence in Wales, of a single specimen displaying microscopic crystal sprays. The mineral was collected in a small section of dumps from weathered veinstone.^[2] In its type locality, it is associated with quartz, galena, sphalerite, melanotektite, willemite, leadhillite, alamosite, larsenite and tennantite. In the Red Gill mine, it appears with quartz, leadhillite, cerussite, caledonite and susannite. It occurs in a partially oxidized lead ore on corroded sulfides from a dolostone-hosted hydrothermal polymetallic ore deposit, or from a hydrothermal lead-zinc-copper ore deposit in a vug in quartz, with other oxidized lead-copper minerals.^[6] In Tsumeb, it grows into bladed crystals on a matrix of lead-copper ores.^[7] It also occurs in post-mining oxidation and weathering deposits. It can also form through post-mining alteration of lead-zinc ore. It is a supergene mineral, meaning it grows close to the surface.^[2]