Adularia
Variety KAlSi3O8
About it
Clear to white potassium feldspar in sharp, wedge-shaped crystals from low-temperature Alpine clefts and veins. Named after the Adula massif in Switzerland; some shows a moonstone-like sheen.
- Type
- Variety
- Group
- Orthoclase variety (feldspar)
- Formula
- KAlSi3O8
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 2.55–2.63
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Monoclinic
- Colours
- colourless, white, pale yellow
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect in two directions at right angles; uneven fracture
Typical values: real specimens vary. For more, see mindat.org.