Holmquistite - Encyclopedia
Class : Silicates
Subclass : Inosilicates
Crystal system : Orthorhombic
Chemistry : Li2Mg3Al2Si8O22(OH)2
Rarity : Uncommon
Holmquistite is a lithium amphibole that forms by metasomatic replacement at the contact between lithium pegmatites and basic rocks. It is a dimorph of clinoholmquistite which forms two series with ferro-holmquistite on the one hand and magnetio-holmquistite on the other. It was named in honor of the Swedish petrologist Johan Holmquist. Holmquistite forms prismatic to acicular crystals that can measure 10 cm, dark purple to black in color, rarely sky blue. It commonly accompanies spodumene, tourmaline and biotite.
Main photo : Holmquistite from Brandrücken, Austria © Christian Auer
Holmquistite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 5 to 6
Density : 2.95 to 3.13
Fracture : Undeterminated
Streak : White to sky blue
TP : Translucent to transparent
RI : 1.613 to 1.666
Birefringence : 0.033 to 0.041
Optical character : Biaxial -
Pleochroism : Strong
Fluorescence : None
Solubility : Insoluble
Magnetism : NoneRadioactivity : None