Holley Blue Agate is a highly sought-after, rare variety of chalcedony known for its intense violet to blue color and high translucency. Found primarily in Linn County, Oregon, it typically occurs as nodules within volcanic host rocks and is cherished by lapidaries for its ability to take a high polish. Its distinctive, rich color makes it one of the most recognizable and valuable agate varieties in North America.
Is this holley 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 holley blue agate with a known reference. Holley 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. Holley Blue Agate leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Holley Blue Agate typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: blue, violet, lavender.
- 5Look at form & habitCrystal system: trigonal. Typical habit: nodular.
Often confused with
Holley Blue Agate vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside holley blue agate
Minerals reported to co-occur with holley 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
- Nodular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Lapidary, Collector, Jewelry
- Host rock
- Volcanic Deposits
- Typical price
- $20-200 per pound of rough, variable for polished specimens
Where rockhounds find holley blue agate
Classic worldwide localities
- Holley, Oregon
- Linn County, Oregon
Field-hunting tip
Look in volcanic deposits country — that is the host setting where holley blue agate typically forms. If you start seeing quartz, zeolites in float, you are in the right ground. Field specimens usually show a nodular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find holley blue agate on the map
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