Logan Sapphire
Image: Chip Clark, Smithsonian staff (Public domain)
Mineral NameLogan Sapphire
Chemical FormulaAl2O3
Mohs Hardness9
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone (parting common)
Fractureconchoidal to uneven
Specific Gravity3.95
Colorsdeep blue, colorless
Transparencytransparent
Type LocalitySri Lanka
Mineral GroupOxides
Usesjewelry, collector
Associated Mineralsdiamond
Raritylegendary
Description
A magnificent cushion-cut deep blue sapphire, weighing 42.29 carats, surrounded by 20 brilliant-cut diamonds, set in a platinum brooch.
Geological Context
Sapphires, a variety of corundum, typically form in metamorphic rocks or as primary minerals in certain igneous rocks, often found in alluvial deposits. Diamonds form deep within the Earth's mantle under extreme pressure and temperature.
