Jeremejevite is a rare aluminum borate mineral with variable fluoride and hydroxide ions. Its chemical formula is Al6B5O15(F, OH)3. It is a hexagonal-dipyramidal mineral containing aluminum, boron, fluorine, hydrogen, and oxygen. It is named after P.V. Jeremejev, Russian mineralogist, and engineer, who first recognized the mineral.
Jeremejevite forms pale blue-green, cornflower-blue, brown or colorless transparent crystals, usually zoned in light hues. Most gem material comes from Namibia.
- Category: Borate mineral
- Formula: Al6B5O15(F, OH)3
- Crystal system: Hexagonal
- Crystal class: Dipyramidal class (6/m)
Jeremejevite produces attractive colorless, yellowish and blue faceted stones which rarely exceed 1 carat in weight. It is a mineral consisting of aluminum borate in colorless or yellowish hexagonal crystals (hardness 6.5, specific gravity 3.28)
- Color: Colorless, white, yellowish, blue
- Crystal habit: Prismatic
- 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 (-)
It was first described in 1883 for an occurrence on Mt. Soktui, Nerschinsk district, Adun-Chilon Mountains, Siberia.
It occurs as a late hydrothermal phase in granitic pegmatites in association with albite, tourmaline, quartz and rarely gypsum. It has also been reported in the Pamir Mountains of Tajikistan, Namibia and the Eifel district, Germany.