Yogo sapphire
Variety Al2O3
About it
Small, evenly coloured cornflower-blue sapphires mined from a dike at Yogo Gulch in central Montana. Unusual among sapphires because they are almost never heated.
- Type
- Variety
- Group
- Corundum variety
- Formula
- Al2O3
- Hardness (Mohs)
- 9
- Specific gravity
- 3.95–4.05
- Streak
- white
- Lustre
- adamantine (diamond-like), vitreous (glassy)
- Crystal system
- Trigonal
- Colours
- cornflower blue, violet-blue
- Transparency
- transparent
- Cleavage and fracture
- none; parting common; conchoidal to uneven fracture
Typical values: real specimens vary. For more, see mindat.org.