Epididymite is a beryllium that is rare mineral that is situated in agpaitic pegmatite intrusions, an unusual igneous rock that has lots of alkaline metals such as sodium and poor in silica. These intrusions also have a great number of unusual elements such as for example beryllium, titanium, fluorine and planet that is rare but are usually low in aluminum and silica. Beryllium is a element that is somewhat exotic in unusual concentrations in agpaite pegmatites allowing Epididymite to form.

Epididymite is located in locations that are famous pegmatite that is agpaitic like Kola Peninsula, Russia; Mont Saint-Hilaire, Canada; Arø Island, Langesundfjord, Norway and Narssârssuk, Greenland. These are well known places for rare silicate minerals. Other Epididymite locations include Vevja quarry, Tvedalen, Norway; Vezná, Czech Republic; near Saint-Amable, Quebec, Canada; near Quincy, Norfolk County, Massachusetts, USA; and crystals which are large Mt. Malosa, Zomba region, Malayi.

Chemical Formula: NaBeSi3O7(OH)
Sodium Beryllium Silicate Hydroxide
Molecular Weight: 245.26 gm
Composition: Sodium 9.37 % Na 12.64 % Na2O
Beryllium 3.67 % Be 10.20 % BeO
Silicon 34.35 % Si 73.49 % SiO2
Hydrogen 0.41 % H 3.67 % H2O
Oxygen 52.19 % O
  100.00 % 100.00 % = TOTAL OXIDE


Crystallography: Orthorhombic – Dipyramidal
Crystal Habit: As pseudohexagonal crystals, tabular on {001}, also elongated along [010], to 6 cm. Micaceous, spherulitic, fine to coarse granular, porcelaneous massive.
Twinning: On {001}, common, simple and polysynthetic; also as trillings.


Cleavage: Perfect on {001}, Distinct on {100}
Fracture: Uneven to Conchoidal when massive
Tenacity: Brittle
Moh’s Hardness: 5.5
Density: 2.55 – 2.61 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive


Color: Colorless, White, also tinted Violet, Blue, or Yellow when finely crystalline
Transparency: Transparent to Translucent 
Luster: Vitreous on fractures, Pearly on cleavages
Refractive Index: 1.536 – 1.546  Biaxial ( + ) or ( – )
Birefringence: 0.0020
Dispersion: Weak