Ruby
Image: James St. John (CC BY 2.0)
Mineral NameRuby
Chemical FormulaAl2O3
Mohs Hardness9
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone (parting present)
Fractureconchoidal
Specific Gravity4
Colorsred, pinkish-red, purplish-red
Transparencytranslucent
Type LocalityPennsylvania, USA
Mineral GroupOxides
Usesjewelry, abrasives, lasers
Associated Mineralsfeldspar, mica, kyanite, garnet, spinel
Rarityrare
Description
This specimen is a large, reddish-brown to pinkish-red crystal, approximately 7.5 centimeters across, exhibiting a somewhat opaque appearance typical of corundum. Its form suggests a hexagonal or trigonal crystal habit.
Geological Context
Ruby forms in metamorphic rocks such as marble, schist, and gneiss, as well as in some igneous rocks like basalt and syenite. It is also frequently found in placer deposits due to its exceptional hardness and resistance to weathering.
