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.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommon

Northupite

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this northupite?

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 northupite with a known reference. Northupite sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Northupite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Northupite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, gray, yellow, brown.
5
Look at form & habit
Crystal system: isometric. Typical habit: octahedral crystals.

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: 2.38 g/cm³
Colors: White Gray Yellow Brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Isometric
Crystal habit: Octahedral Crystals
Cleavage: None
Rarity: Uncommon
Uses: Collector
Host rock: Evaporite Deposits in Alkaline Lake Beds
Typical price: $20-150 for thumbnail to cabinet specimens

Where rockhounds find northupite

Classic worldwide localities

Searles Lake, California, USA
Green River Formation, Wyoming, USA
Lake Katwe, Uganda

Field-hunting tip

Look in evaporite deposits in alkaline lake beds country — that is the host setting where northupite typically forms. If you start seeing gaylussite, trona, halite in float, you are in the right ground. Field specimens usually show a octahedral crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify northupite?+

Mohs hardness is 3.5-4. It typically shows a vitreous luster. The streak is white. Common colors include white, gray, yellow, brown.

Where is northupite found?+

Notable localities include Searles Lake, California, USA; Green River Formation, Wyoming, USA; Lake Katwe, Uganda.

How much is northupite worth?+

Typical asking prices fall in the range of $20-150 for thumbnail to cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like northupite?+

Northupite is most often confused with Tychite, Shortite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with northupite?+

Northupite commonly co-occurs with Gaylussite, Trona, Halite, Borax, Tychite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does northupite form in?+

Northupite typically forms in evaporite deposits in alkaline lake beds. Working float back to the host body is the standard way to chase a fresh occurrence.

What is northupite used for?+

Northupite is used in collector.

Find northupite on the map

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