Blue John
Variety CaF2
Take care.
- Sensitive to heat: Keep it away from heat and sudden changes of temperature, including hot lights and ultrasonic cleaners.
About it
Banded purple-blue and yellow fluorite found only near Castleton, Derbyshire, England. Mined in small amounts for vases and jewellery, it is usually stabilized with resin before cutting.
- Type
- Variety
- Group
- Fluorite variety
- Formula
- CaF2
- Hardness (Mohs)
- 4
- Specific gravity
- 3.18
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Isometric (cubic)
- Colours
- purple-blue, yellow, white, in bands
- Transparency
- translucent, opaque
- Cleavage and fracture
- perfect octahedral
Typical values: real specimens vary. For more, see mindat.org.