Epididymite - Encyclopedia
Class : Silicates
Subclass : Inosilicates
Crystal system : Orthorhombic
Chemistry : NaBeSi3O7(OH)
Rarity : Rare
Epididymite is a rare sodium beryllium silicate, dimorphic from eudidymite. It is a mineral found in pegmatites of nepheline syenites, associated in particular with albite, aegyrine, nepheline and eudialyte. It takes its name from the Greek epi (near) and didumos (twin) due to the existence of its dimorph. Epididymite forms centimeter-sized tabular pseudo-hexagonal crystals, micaceous or spherolitic aggregates with a fibroradiated texture, or porcelanose masses. Usually colorless to white, epididymite can also be shades of purple, bluish or yellow when it is finely crystallized.
Main photo : Epididymite of Poudrette Quarry, Mont St-Hilaire, Quebec, Canada © Martin Slama
Epididymite in the World
Twinning
Twins are known in reticulated crystals and pseudo-hexagonal trills.
Fakes and treatments
No fake listed for this mineral species.
Hardness : 5.5
Density : 2.54
Fracture : Irregular to conchoidal
Streak : White
TP : Translucent to transparent
RI : 1.544 to 1.546
Birefringence : 0.002
Optical character : Biaxial +
Pleochroism : None
Fluorescence : Sometimes green
Solubility : Hydrofluoric acid
Magnetism : None
Radioactivity : None