Nahcolite is a natural form of sodium bicarbonate that typically occurs in saline evaporite deposits. It is often found as transparent to white crystals or crusts and is highly soluble in water, meaning collectors should store it in a dry environment. It is most famously associated with the Green River Formation, where it occurs in significant beds alongside other evaporite minerals.
Is this nahcolite?
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 nahcolite with a known reference. Nahcolite sits at Mohs 2.5, 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, resinous on cleavages.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, fibrous, tabular, botryoidal crusts.
Often confused with
Nahcolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside nahcolite
Minerals reported to co-occur with nahcolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaHCO₃
- Mohs hardness
- 2.5
- Density
- 2.21-2.238 g/cm³
- Streak
- White
- Luster
- Vitreous, resinous on cleavages
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, fibrous, tabular, botryoidal crusts
- Cleavage
- Perfect on {101}; good on {111}; fair on {100}
- Fluorescence
- Blue-white cream-yellow under SW UV; cream-yellow under LW UV
- Rarity
- Uncommon
- Uses
- Collector, Industrial, Research
- Host rock
- A precipitate from hot springs; as efflorescences around saline lakes and in brines; formed at a late stage in differentiated alkalic massifs; as a solid in liquid inclusions in a variety of other mineral species
Where rockhounds find nahcolite
Classic worldwide localities
- Searles Lake, San Bernardino Co., California, USA
- Green River Formation, Colorado and Utah, northwestern Colorado having estimated reserves of over 30 billion tons, USA
- A Roman conduit at Stufe de Nerone, Campi Flegrei, near Naples, and on Vesuvius, Campania, Italy
- Tincalayu deposit, Salar del Hombre Muerto, Salta Province, Argentina
- Ilmajok River and on Mt. Alluaiv, Lovozero massif, and at Tuliylukht Bay and on Mt. Kukisvumchorr, Khibiny massif, Kola Peninsula, Russia
- Mt. Erebus, Victoria Land, Antarctica
Field-hunting tip
Where it forms: A precipitate from hot springs; as efflorescences around saline lakes and in brines; formed at a late stage in differentiated alkalic massifs; as a solid in liquid inclusions in a variety of other mineral species. If you start seeing trona, thermonatrite, thénardite in float, you are in the right ground. Typical habit: prismatic crystals, fibrous, tabular, botryoidal crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify nahcolite?+
Where is nahcolite found?+
What rocks look like nahcolite?+
What minerals are found with nahcolite?+
What kind of rock does nahcolite form in?+
What is nahcolite used for?+
Find nahcolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
