RockHoundR

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.

Hardness
7
Mohs
Luster
Vitreous
Streak
White
Transparency
Transparent

Is this pecos diamond?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

  • 1
    Test the hardness
    Try 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.
  • 2
    Check the streak
    Drag the specimen across an unglazed porcelain plate. Streak: white.
  • 3
    Read the luster
    Hold the specimen under a strong light. Luster: vitreous.
  • 4
    Match the color range
    Compare against the expected color range: clear, colorless, red, brown.
  • 5
    Look at form & habit
    Crystal 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.

Herkimer diamond with a natural point at both ends and bright untreated faces
mineral
Herkimer Diamond
Mohs 7
Compare →

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
Colors
ClearColorlessRedBrown
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 spots

Classic worldwide localities

  • Pecos River Valley, New Mexico, USA
  • Eddy County, New Mexico, USA
  • Chaves County, New Mexico, USA

Field-hunting tip

Where it forms: sedimentary evaporite deposits. If you start seeing gypsum, dolomite, calcite in float, you are in the right ground. Typical habit: doubly terminated prismatic crystals. 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.

Browse 4 U.S. spots for pecos diamond →

Common questions

How do you identify pecos diamond?+
Mohs hardness is 7. Luster: vitreous. The streak is white. Common colors include clear, colorless, red, brown.
Where is pecos diamond found?+
Notable localities include Pecos River Valley, New Mexico, USA; Eddy County, New Mexico, USA; Chaves County, New Mexico, USA.
Can I find pecos diamond in the United States?+
RockHoundR maps 4 pecos diamond rockhounding spots across 1 U.S. states. The top states are New Mexico.
What rocks look like pecos diamond?+
Pecos Diamond is most often confused with Herkimer Diamond. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with pecos diamond?+
Pecos Diamond commonly co-occurs with gypsum, dolomite, calcite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does pecos diamond form in?+
Where it forms: sedimentary evaporite deposits. Working float back to the host body is the standard way to chase a fresh occurrence.
What is pecos diamond used for?+
Pecos Diamond is used in collector, lapidary.

Find pecos diamond on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.

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