HELVINE
Class : Silicates
Subclass : Tectosilicates
Crystal system : Cubic
Chemistry : Mn4Be3(SiO4)3S
Rarity : Quite common
Helvine (or helvite) is a complex silicate of beryllium and manganese which is found in various contexts : granites and their pegmatites, pegmatites of nepheline syenites, hydrothermal veins, tactites and skarns. It is a mineral which forms two continuous series : with genthelvite (zinciferous) and danalite (ferriferous). Its name comes from the Greek helios (sun) in reference to its main color. However, helvine is varied in color : gray-yellow to yellow and orange, brown-red, sometimes green-yellow. It essentially forms tetrahedra, sometimes pseudo-octahedra reaching up to 12 cm in edge and xenomorphic masses. It is very occasionally a beryllium ore.
Main photo : Helvine from Huanggang Mine, Inner Mongolia, China © Jordy Fabre
Helvine in the World
Twinning
Interpenetration twins are known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species, but very difficult to differentiate from genthelvite and danalite without chemical analysis.
Hardness : 6 to 6.5
Density : 3.2 to 3.44
Fracture : Irregular to conchoidal
Streak : White
TP : Translucent
RI : 1.728 to 1.749
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : None
Solubility : Hydrochloric acid
Magnetism : NoneRadioactivity : None