Goldschmidtite is a rare potassium niobium oxide, typically dark green. It was approved as a distinct mineral species in 2018. It was first described from Koffiefontein kimberlite pipe, ~ 80 km SSE of Kimberley, Kaapvaal Craton, South Africa.
Is this goldschmidtite?
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 goldschmidtite with a known reference. Goldschmidtite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Goldschmidtite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Goldschmidtite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: dark green.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral to subhedral grains.
Often confused with
Goldschmidtite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Goldschmidtite is noticeably harder (Mohs 3.5 vs. 1.5-2); streak differs, so Goldschmidtite leaves black, Sylvanite leaves gray; luster reads adamantine on Goldschmidtite and metallic on Sylvanite.
How to tell apart: Streak differs, so Goldschmidtite leaves black, Calaverite leaves yellowish-green; luster reads adamantine on Goldschmidtite and metallic on Calaverite.
Often found alongside goldschmidtite
Minerals reported to co-occur with goldschmidtite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,REE,Sr)(Nb,Cr)O₃
- Mohs hardness
- 3.5
- Density
- 5.32 g/cm³
- Colors
- Streak
- Black
- Luster
- Adamantine
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Anhedral to Subhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Kimberlite
Where rockhounds find goldschmidtite
Classic worldwide localities
- Koffiefontein mine, South Africa
Field-hunting tip
Look in kimberlite country, the host setting where goldschmidtite typically forms. If you start seeing diamond, phlogopite, enstatite in float, you are in the right ground. Field specimens usually show a anhedral to subhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify goldschmidtite?+
Where is goldschmidtite found?+
What rocks look like goldschmidtite?+
What minerals are found with goldschmidtite?+
What kind of rock does goldschmidtite form in?+
What is goldschmidtite used for?+
Find goldschmidtite on the map
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