Cuatrocapaite-(NH4) is a very rare ammonium copper sulfate mineral first identified in evaporite deposits in Mexico. It typically occurs as small, pale yellow, platy crystals forming in arid environments and is highly sought after by advanced mineral collectors.
Is this cuatrocapaite-(nh4)?
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 cuatrocapaite-(nh4) with a known reference. Cuatrocapaite-(NH4) sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cuatrocapaite-(NH4) leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cuatrocapaite-(NH4) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals.
Often found alongside cuatrocapaite-(nh4)
Minerals reported to co-occur with cuatrocapaite-(nh4). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₄Cu₂(SO₄)₃
- Mohs hardness
- 2
- Density
- 2.44 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- expensive due to rarity
Where rockhounds find cuatrocapaite-(nh4)
Classic worldwide localities
- Cuatro Cienegas, Coahuila, Mexico
Field-hunting tip
Look in evaporite deposits country — that is the host setting where cuatrocapaite-(nh4) typically forms. If you start seeing gypsum, thenardite in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.


