crystals of joaquinite-(Ce), crystals of neptunite, natrolite : Dallas Gem Mine (Benitoite Mine ; Benitoite Gem Mine ; Gem Mine), Dallas Gem Mine area, San Beni — Photo: Parent Géry · CC BY-SA 3.0
Natrolite
A sodium zeolite forming slender white needles in basalt cavities — type locality Hohentwiel, Germany.
Intro adapted from Wikipedia (CC BY-SA).
Natrolite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂(Si₃Al₂)O₁₀·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Fdd2). It is a member of the Natrolite structural group.
Key properties: Mohs hardness 5–5.5; specific gravity 2.2–2.26; typically white or colorless or yellow or pink; white streak; Vitreous to pearly luster; optically biaxial.
IMA symbol Ntr, IMA status: approved, named in 1803.
Found in cavities in amygdaloidal basalts and related igneous rocks, one of the last minerals to form; fills seams in granite, gneiss, and syenite.
It is found associated with Zeolites, calcite, nepheline, sodalite, quartz.
The name comes from the Latin natron, for the sodium content.
Collections: Collector Favorites.