Heulandite
Mineral (Ca,Na2)Al2Si7O18·6H2O
Also called Heulandite-Ca and Heulandite-Na
About it
Coffin-shaped tabular crystals with a strong pearly lustre on one face; bright red heulandite from Italy's Val di Fassa and peach to green crystals from Indian basalts.
- Type
- Mineral
- Group
- Silicate (tectosilicate), zeolite group
- Formula
- (Ca,Na2)Al2Si7O18·6H2O
- Hardness (Mohs)
- 3.5–4
- Specific gravity
- 2.1–2.2
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Monoclinic
- Colours
- white, colourless, pink, red, orange, yellow, brown
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in one direction
Typical values: real specimens vary. For more, see mindat.org.