gemstone

Ruby (faceted)

Corundum (Al2O3 with chromium traces)

Hardness: 9 on Mohs scale; Color: Deep pinkish-red to pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal (Hexagonal scalenohedral); Cleavage: None; Specific Gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Deep pinkish-red to pigeon-blood red
Luster: Vitreous to sub-adamantine

Identified July 10, 2026More gemstone →

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Physical properties

Formation & geological history

Found in metamorphic rocks such as marble or gneiss, and in alluvial deposits. Formed under high heat and pressure in the Earth's crust, often in Tertiary period deposits.

Uses & applications

Primarily used as a high-value gemstone in jewelry. Historically used in watch bearings and precision instruments due to its extreme hardness.

Geological facts

Ruby is the most valuable variety of the corundum mineral. The presence of chromium is what gives it the red color; if it were any other color, it would be called a sapphire.

Field identification & locations

Identify in the field by its high hardness (it can scratch almost any other mineral except diamond) and hexagonal crystal habit in raw form. Often found in Myanmar, Sri Lanka, and Thailand.

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Cubic Zirconia (or possibly Diamond)

Zirconium dioxide (or Carbon)

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Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

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Faceted Gemstone

Unknown transparent mineral, possibly Diamond (C), Cubic Zirconia (ZrO2), Quartz (SiO2), or Glass

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Milky Quartz

Silicon Dioxide (SiO2)

mineral