Image: James St. John (CC BY 2.0)
trigonalrareOxides
Ruby
Al2O3
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.
Ruby Physical Properties
Mohs Hardness
9Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
none (parting present)Fracture
conchoidalSpecific Gravity
4Colors
red, pinkish-red, purplish-redTransparency
translucentType Locality
Pennsylvania, USAMineral Group
OxidesUses
jewelry, abrasives, lasersAssociated Minerals
feldspar, mica, kyanite, garnet, spinelRarity
rareGeological 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.
