Logan Sapphire
Image: Chip Clark, Smithsonian staff (Public domain)
Mineral NameLogan Sapphire
Chemical FormulaAl2O3
Mohs Hardness9
Crystal Systemtrigonal
Lusteradamantine
Streak Colorwhite
Cleavagenone (parting present)
Fractureconchoidal to uneven
Specific Gravity3.95
Colorsdeep blue
Transparencytransparent
Type LocalitySri Lanka (Ceylon)
Mineral GroupOxides
Usesjewelry, collector
Associated Mineralsdiamond
Raritylegendary
Description
A magnificent cushion-cut deep blue sapphire, weighing 42.29 carats, set in a brooch and surrounded by 20 brilliant-cut diamonds.
Geological Context
Sapphires, a variety of corundum, typically form in metamorphic rocks such as marble or gneiss, or in certain igneous rocks like basalt or pegmatite, often found in alluvial deposits due to their hardness and resistance to weathering.
