Jeremejevite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Jeremejevite
Jeremjevite colorless needles - Ochtendung, Eifel, Germany.jpg
Jeremjevite colorless to light blue crystal spray of prisms from Ochtendung, Eifel, Germany
General
Category Borate mineral
Formula
(repeating unit)
Al6B5O15(F,OH)3
Strunz classification 06.AB.15
Crystal symmetry Hexagonal dipyramidal
H-M symbol: (6/m)
Space group: P 63/m
Unit cell a = 8.5591(3) Å, c = 8.1814(6) Å; Z=2
Identification
Color Colorless, white, yellowish, blue
Crystal habit Prismatic
Crystal system Hexagonal
Cleavage None observed
Fracture Conchoidal
Mohs scale hardness 6.5 - 7.5
Luster Vitreous
Streak White
Diaphaneity Transparent
Specific gravity 3.28 - 3.31
Optical properties Uniaxial (-)
Refractive index nω = 1.653 nε = 1.640
Birefringence 0.0130
Pleochroism Colorless - light blue-violet
Other characteristics Piezoelectric
References [1][2][3]

Jeremejevite is a rare aluminium borate mineral with variable fluoride and hydroxide ions. Its chemical formula is Al6B5O15(F,OH)3.

It was first described in 1883 for an occurrence on Mt. Soktui, Nerschinsk district, Adun-Chilon Mountains, Siberia. It was named after Russian mineralogist Pavel Vladimirovich Eremeev (Jeremejev, German) (1830–1899).[3]

It occurs as a late hydrothermal phase in granitic pegmatites in association with albite, tourmaline, quartz and rarely gypsum. It has also been reported from the Pamir Mountains of Tajikistan, Namibia and the Eifel district, Germany.[3]

References[edit]

Blue Jeremejevite in rare, clear crystal form. Image width: 1.5 mm.