Blue sapphire is the highly prized, iron and titanium-bearing gem variety of corundum. Collectors look for strong, vibrant blue saturation and often seek crystals with characteristic hexagonal growth lines or rutile silk inclusions.
Is this blue sapphire?
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 blue sapphire with a known reference. Blue Sapphire 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: colorless.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue, violet-blue, greenish-blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: hexagonal bipyramidal crystals, barrel-shaped.
Often confused with
Blue Sapphire vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Blue Sapphire is noticeably harder (Mohs 9 vs. 6.5-7); streak differs, so Blue Sapphire leaves colorless, Tanzanite leaves white.
How to tell apart: Blue Sapphire is noticeably harder (Mohs 9 vs. 6-6.5); streak differs, so Blue Sapphire leaves colorless, Benitoite leaves white.
How to tell apart: Blue Sapphire is noticeably harder (Mohs 9 vs. 7-7.5); streak differs, so Blue Sapphire leaves colorless, Cordierite leaves white.
Often found alongside blue sapphire
Minerals reported to co-occur with blue sapphire. 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
- 3.98-4.06 g/cm³
- Streak
- Colorless
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Hexagonal bipyramidal crystals, barrel-shaped
- Cleavage
- None
- Rarity
- Common
- Uses
- Gemstone, Jewelry, Collector
- Host rock
- pegmatites, basalt-related alluvial deposits, metamorphic marbles
Where rockhounds find blue sapphire
1 mapped spotsClassic worldwide localities
- Sri Lanka
- Myanmar
- Madagascar
- Kashmir
- Thailand
Field-hunting tip
Where it forms: pegmatites, basalt-related alluvial deposits, metamorphic marbles. If you start seeing spinel, garnet, zircon in float, you are in the right ground. Typical habit: hexagonal bipyramidal crystals, barrel-shaped. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in North Carolina. Start trip planning there.
Common questions
How do you identify blue sapphire?+
Where is blue sapphire found?+
Can I find blue sapphire in the United States?+
What rocks look like blue sapphire?+
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Find blue sapphire on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
