Blue Agate is a translucent variety of chalcedony characterized by its distinct fine banding in shades of light blue, white, and grey. It typically forms within the gas cavities of volcanic rocks, where silica-rich fluids deposited layers over time. Collectors look for pieces with high clarity and well-defined, intricate banding patterns.
Is this blue agate?
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 agate with a known reference. Blue Agate sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Blue Agate leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Blue Agate typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: blue, white, gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: banded, massive, botryoidal.
Often confused with
Blue Agate vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads waxy on Blue Agate and vitreous on Blue Lace Agate.
How to tell apart: Blue Agate is noticeably harder (Mohs 6.5-7 vs. 4-4.5); luster reads waxy on Blue Agate and vitreous on Smithsonite.
Often found alongside blue agate
Minerals reported to co-occur with blue agate. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Banded, Massive, Botryoidal
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Decorative, Collector
- Host rock
- Volcanic Cavities
- Typical price
- $5-50 for small slabs or cabochons, $20-200 for specimens
Where rockhounds find blue agate
7 mapped spotsClassic worldwide localities
- Namibia
- Brazil
- USA
- India
Field-hunting tip
Look in volcanic cavities country — that is the host setting where blue agate typically forms. If you start seeing quartz, calcite, zeolites in float, you are in the right ground. Field specimens usually show a banded, massive, botryoidal habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California, Arizona, Idaho — start trip planning there.
Common questions
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Find blue agate on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
