Ruby is the red, gem-quality variety of corundum, colored primarily by trace amounts of chromium. It is highly valued for its intense color, extreme hardness, and lack of cleavage, making it a premier gemstone for jewelry collectors.
Is this ruby?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch ruby with a known reference. Ruby sits at Mohs 9, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: red.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular hexagonal prisms.
Often confused with
Ruby vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ruby
Minerals reported to co-occur with ruby. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂O₃
- Mohs hardness
- 9
- Density
- 4.0 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Tabular hexagonal prisms
- Cleavage
- None
- Fluorescence
- Bright red under UV
- Rarity
- Rare
- Uses
- Gemstone, Collector
- Host rock
- marble, basalt, and secondary alluvial deposits
Where rockhounds find ruby
26 mapped spotsClassic worldwide localities
- Mogok, Myanmar
- Jagdalek, Afghanistan
- Ratnapura, Sri Lanka
- Montepuez, Mozambique
U.S. states with ruby
Each link opens a state-specific list of mapped rockhounding spots that produce ruby.
Field-hunting tip
Where it forms: marble, basalt, and secondary alluvial deposits. If you start seeing calcite, phlogopite, spinel in float, you are in the right ground. Typical habit: tabular hexagonal prisms. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in North Carolina, Georgia, Wyoming. Start trip planning there.
More ruby photos
Common questions
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Find ruby on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
