Pirssonite is a rare hydrated sodium calcium carbonate mineral that typically forms as sharp, wedge-shaped or tabular crystals in evaporite environments. It is most famous for its occurrence in the alkaline brine deposits of Searles Lake, where it is found associated with other rare carbonates and sulfates. Collectors prize it for its distinct crystal geometry and transparency, though it is prone to dehydration if kept in very dry conditions.
Is this pirssonite?
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 pirssonite with a known reference. Pirssonite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, grayish, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular to prismatic crystals, often wedge-shaped.
Often confused with
Pirssonite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pirssonite
Minerals reported to co-occur with pirssonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Ca(CO₃)₂·2H₂O
- Mohs hardness
- 3-3.5
- Density
- 2.352-2.382 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular to prismatic crystals, often wedge-shaped
- Cleavage
- None
- Fluorescence
- Weak Blue-white to blue-gray under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare component of saline lake-bed sediments; in a differentiated alkalic massif
Where rockhounds find pirssonite
Classic worldwide localities
- Searles Lake, San Bernardino Co., at Borax Lake, Lake Co., in Deep Spring Lake, Inyo Co., and at Owens Lake, Mono Co., California, USA
- John Hay, Jr. Well No. 1, about 30 km west of Green River, Sweetwater Co., Wyoming, USA
- Arizaro, Pastos Grandes, and Pozuelos playas, Salta Province, Argentina
- Jequetepeque River Valley, northwest Peru
- Otjiwalundo Salt Pan, about 400 km west-northwest of Otavi, Namibia
- Beypazari Basin, Ankara, Turkey
Field-hunting tip
Where it forms: A rare component of saline lake-bed sediments; in a differentiated alkalic massif. If you start seeing northupite, trona, gaylussite in float, you are in the right ground. Typical habit: tabular to prismatic crystals, often wedge-shaped. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pirssonite?+
Where is pirssonite found?+
What rocks look like pirssonite?+
What minerals are found with pirssonite?+
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What is pirssonite used for?+
Find pirssonite on the map
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