Blue chalcedony is a cryptocrystalline variety of quartz prized for its soothing, sky-blue color caused by light scattering. It is typically found forming botryoidal or massive habits in volcanic cavities and is a favorite for cabochon cutting due to its toughness and translucent finish.
Is this blue chalcedony?
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 chalcedony with a known reference. Blue Chalcedony 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 Chalcedony leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Blue Chalcedony typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: blue, light blue, grayish blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal, massive, crusts.
Often confused with
Blue Chalcedony vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads waxy on Blue Chalcedony and vitreous on Blue Lace Agate.
How to tell apart: Blue Chalcedony is noticeably harder (Mohs 6.5-7 vs. 4-4.5); luster reads waxy on Blue Chalcedony and vitreous on Smithsonite.
How to tell apart: Blue Chalcedony is noticeably harder (Mohs 6.5-7 vs. 4.5-5); luster reads waxy on Blue Chalcedony and vitreous on Hemimorphite.
Often found alongside blue chalcedony
Minerals reported to co-occur with blue chalcedony. 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
- 2.58-2.64 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal, Massive, Crusts
- Cleavage
- None
- Rarity
- Common
- Uses
- Gemstone, Lapidary, Decorative, Collector
- Host rock
- Hydrothermal Veins and Volcanic Cavities
- Typical price
- $10-50 for cabs, $50-300 for high-quality specimens
Where rockhounds find blue chalcedony
4 mapped spotsClassic worldwide localities
- Turkey
- Namibia
- USA
- Iceland
- Malawi
Field-hunting tip
Look in hydrothermal veins and volcanic cavities country — that is the host setting where blue chalcedony typically forms. If you start seeing quartz, calcite, zeolites in float, you are in the right ground. Field specimens usually show a botryoidal, massive, crusts habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in South Dakota, Nebraska, New Mexico — start trip planning there.
Common questions
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Find blue chalcedony on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
