Congolite is a rare member of the boracite group typically found in salt dome environments. Collectors should look for its distinctive pseudo-cubic trigonal crystals, which are frequently associated with potash-bearing evaporite sequences.
Is this congolite?
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 congolite with a known reference. Congolite sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Congolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Congolite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, pale pink.
- 5Look at form & habitCrystal system: trigonal. Typical habit: equant pseudo-cubic crystals, massive.
Often confused with
Congolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside congolite
Minerals reported to co-occur with congolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₃Mg₃(B₇O₁₃)Cl
- Mohs hardness
- 7
- Density
- 3.31 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Equant Pseudo-cubic Crystals, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find congolite
Classic worldwide localities
- Republic of the Congo
- Kazakhstan
- Russia
Field-hunting tip
Look in evaporite deposits country, the host setting where congolite typically forms. If you start seeing halite, sylvite, carnallite in float, you are in the right ground. Field specimens usually show a equant pseudo-cubic crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find congolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
