Fluorapophyllite-(K)
Mineral KCa4Si8O20F·8H2O
Also called Apophyllite, Fluorapophyllite, and Fish-eye stone
About it
Blocky prisms and pyramids with a pearly top face, in basalt cavities; green crystals with stilbite from Pune, India, are classics, and pink ones from Mexico's Guanajuato.
- Type
- Mineral
- Group
- Silicate (phyllosilicate), apophyllite group
- Formula
- KCa4Si8O20F·8H2O
- Hardness (Mohs)
- 4.5–5
- Specific gravity
- 2.33–2.37
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Tetragonal
- Colours
- colourless, white, green, pink, yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in one direction (basal)
Typical values: real specimens vary. For more, see mindat.org.