A Pecos Diamond is a small, doubly terminated quartz crystal found in the gypsum and dolomite beds of the Pecos River Valley. It is known for a shape that mimics a cut gemstone, and usually occurs as a loose, individual crystal weathered out of the surrounding sedimentary rock.
Is this pecos diamond?
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 pecos diamond with a known reference. Pecos Diamond 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. Pecos Diamond leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Pecos Diamond typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: clear, colorless, red, brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: doubly terminated prismatic crystals.
Often confused with
Pecos Diamond vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pecos diamond
Minerals reported to co-occur with pecos diamond. 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
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Doubly Terminated Prismatic Crystals
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Sedimentary Evaporite Deposits
Where rockhounds find pecos diamond
4 mapped spotsClassic worldwide localities
- Pecos River Valley, New Mexico, USA
- Eddy County, New Mexico, USA
- Chaves County, New Mexico, USA
Field-hunting tip
Look in sedimentary evaporite deposits country, the host setting where pecos diamond typically forms. If you start seeing gypsum, dolomite, calcite in float, you are in the right ground. Field specimens usually show a doubly terminated prismatic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico. Start trip planning there.
Common questions
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Find pecos diamond on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
