Piypite

Piypite
Green acicular crystals of piypite
General
Category	Sulfate mineral
Formula (repeating unit)	K2Cu2O(SO4)2
IMA symbol	Piy[1]
Strunz classification	7.BC.40
Crystal system	Tetragonal
Crystal class	Pyramidal (4) H-M symbol: (4)
Space group	I4
Unit cell	a = 13.6 Å, c = 4.95 Å; Z = 2
Identification
Color	Emerald-green, dark green, black
Crystal habit	Acicular crystals elongated along [001], square cross section, commonly hollow; also as mosslike aggregates
Cleavage	Perfect, parallel to elongation
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Vitreous to greasy
Streak	Yellowish green
Diaphaneity	Transparent to translucent
Specific gravity	3.0 - 3.1
Optical properties	Uniaxial (+)
Refractive index	nω = 1.583 nε = 1.695
Birefringence	δ = 0.112
Pleochroism	Distinct; O = pale green, yellowish green; E = deep green, pale yellowish green
Solubility	Soluble in water, leaves residue
References	[2][3][4][5]

Piypite is a rare potassium, copper sulfate mineral with formula: K₂Cu₂O(SO₄)₂. It crystallizes in the tetragonal system and occurs as needlelike crystals and masses. Individual crystals are square in cross-section and often hollow. It is emerald green to black in color with a vitreous to greasy luster.^[3][4]

It was first described in 1982 for an occurrence in the Main Fracture of the Tolbachik volcano, Kamchatka Oblast, Russia. It has also been reported from Mount Vesuvius, Italy, and in a slag deposit in the Bad Ems District in the Rhineland-Palatinate, Germany.^[3][2] Piypite occurs as a sublimate phase in a fumarole environment. Associated minerals include halite, sylvite, langbeinite, tenorite, hematite, , , urusovite, aphthitalite, , cotunnite, , , euchlorine, , , alarsite, , and lammerite at the type locality in Kamchatka. On Vesuvius, it occurs with paratacamite.^[3]

References[]