Northupite is a rare carbonate mineral typically found as sharp, glassy octahedral crystals embedded in evaporite beds. It is most famously associated with the saline deposits of Searles Lake in California, where it forms in hypersaline, alkaline brines.
Is this northupite?
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 northupite with a known reference. Northupite sits at Mohs 3.5-4, 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: brownish, colorless, gray, gray brown, yellow.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, pyramidal.
Often confused with
Northupite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside northupite
Minerals reported to co-occur with northupite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃Mg(CO₃)₂Cl
- Mohs hardness
- 3.5-4
- Density
- 2.380-2.407 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Crystalline, pyramidal
- Cleavage
- None
- Fluorescence
- Bright cream white under LW UV
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- An uncommon mineral, formed probably between 20°C and 50°C, as a lacustrine deposit or at depth in mud and clay; may be primary or a replacement of earlier saline minerals
Where rockhounds find northupite
Classic worldwide localities
- Searles Lake, San Bernardino Co., and Borax Lake, Lake Co., California, USA
- John Hay, Jr. Well No. 1 and the Westvaco trona mine, about 30 km west of Green River, Sweetwater Co., Wyoming, USA
- Lake Katwe and Lake Mahega, Uganda
- Kanem region, near Lake Chad, Chad
- Tuzla salt mine, Bosnia-Herzegovina
- Mt. Erebus, Victoria Land, and on Ross Island, Ross Sea, Antarctica
Field-hunting tip
Where it forms: An uncommon mineral, formed probably between 20°C and 50°C, as a lacustrine deposit or at depth in mud and clay; may be primary or a replacement of earlier saline minerals. If you start seeing tychite, pirssonite, shortite in float, you are in the right ground. Typical habit: crystalline, pyramidal. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify northupite?+
Where is northupite found?+
What rocks look like northupite?+
What minerals are found with northupite?+
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What is northupite used for?+
Find northupite on the map
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