Trona is a primary ore of sodium carbonate, commonly forming as evaporite deposits in arid lake beds. It is easily recognized by its bladed, often translucent crystal clusters, though it can also appear as massive or efflorescent crusts that crumble if exposed to excessive humidity.
Is this trona?
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 trona with a known reference. Trona sits at Mohs 2.5-3, 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, gray white, grayish, yellowish, yellowish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: columnar, fibrous, massive.
Often confused with
Trona vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside trona
Minerals reported to co-occur with trona. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃(CO₃)(HCO₃)·2H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.11 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Columnar, fibrous, massive
- Cleavage
- {100}, perfect; {211} and {001}, interrupted
- Fluorescence
- Blue-white yellow-orange under SW UV; bright blue white yellow-orange under LW UV
- Rarity
- Common
- Uses
- Industrial, Collector
- Host rock
- Deposited from saline lakes and along river banks as efflorescences in arid climates; rarely from fumarolic action
Where rockhounds find trona
Classic worldwide localities
- Searles Lake, San Bernardino Co., Borax Lake, Lake Co., and Owens Lake, Inyo Co., California, USA
- Extensive deposits, aggregating over 100 billion tons, occur in the Green River Formation, Wyoming, Colorado, Utah, USA
- Little Soda Lake, Churchill Co., Nevada, USA
- Lower Nile delta, near Memphis, Egypt, in the Sahara Desert, Africa
- Lake Magadi, Kenya, about which 2 billion tons have formed
- Lake Chad, Chad
Field-hunting tip
Where it forms: Deposited from saline lakes and along river banks as efflorescences in arid climates; rarely from fumarolic action. If you start seeing natron, thermonatrite, halite in float, you are in the right ground. Typical habit: columnar, fibrous, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find trona on the map
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