Ellensburg Blue is a highly prized, rare variety of chalcedony found exclusively in the volcanic gravels of Kittitas County, Washington. It is famous for its distinct cornflower blue color, which is attributed to light scattering from microscopic inclusions rather than chemical impurities. Collectors prize it for its translucency and depth of color, though high-quality specimens are increasingly difficult to find.
Is this ellensburg blue?
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 ellensburg blue with a known reference. Ellensburg Blue sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ellensburg Blue leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ellensburg Blue typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, violet-blue, cornflower blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Ellensburg Blue vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ellensburg blue
Minerals reported to co-occur with ellensburg blue. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Gemstone, Lapidary, Collector
- Host rock
- Volcanic Basalt
- Typical price
- $50-500 per gram depending on saturation and clarity
Where rockhounds find ellensburg blue
Classic worldwide localities
- Kittitas County, Washington, USA
- Manastash Ridge, Washington, USA
Field-hunting tip
Look in volcanic basalt country — that is the host setting where ellensburg blue typically forms. If you start seeing basalt, quartz, zeolites in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ellensburg blue on the map
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