Howlite
Mineral Ca2B5SiO9(OH)5
About it
White, chalky nodules with a web of grey to black veins, usually cut as beads and often dyed to imitate turquoise. Named for Henry How of Nova Scotia; nodules come from California and Nova Scotia.
- Type
- Mineral
- Group
- Borate (borosilicate)
- Formula
- Ca2B5SiO9(OH)5
- Hardness (Mohs)
- 3.5
- Specific gravity
- 2.53–2.59
- Streak
- white
- Lustre
- subvitreous, dull
- Crystal system
- Monoclinic
- Colours
- white, grey, with grey to black veins
- Transparency
- opaque, translucent
- Cleavage and fracture
- none; uneven to conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.