Paceite is an exceptionally rare calcium copper acetate mineral discovered in the Pace Pit of Kentucky. It typically forms as small, clear, tabular crystals in association with secondary copper minerals within weathered carbonate rocks.
Is this paceite?
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 paceite with a known reference. Paceite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: encrustations, water soluble.
Often confused with
Paceite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Calcite is the harder of the two (Mohs 3 vs. 1.5); streak differs, so Paceite leaves pale blue, Calcite leaves white.
How to tell apart: Streak differs, so Paceite leaves pale blue, Gypsum leaves white; luster reads vitreous on Paceite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
Often found alongside paceite
Minerals reported to co-occur with paceite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCu(CH₃COO)₄·6H₂O
- Mohs hardness
- 1.5
- Density
- 1.472 g/cm³
- Colors
- Streak
- Pale blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Encrustations, water soluble
- Cleavage
- On {100} and {110}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed in ferruginous gossan by reaction of oxidized zone metallic minerals with decaying vegetable matter provided by leaf litter and possibly mine timbers
Where rockhounds find paceite
Classic worldwide localities
- Potosi Ag–Pb–Zn mine, two km northeast of Broken Hill, New South Wales, Australia
Field-hunting tip
Where it forms: Formed in ferruginous gossan by reaction of oxidized zone metallic minerals with decaying vegetable matter provided by leaf litter and possibly mine timbers. If you start seeing hoganite, linarite, malachite in float, you are in the right ground. Typical habit: encrustations, water soluble. Train your eye for that shape before scanning the outcrop.
Common questions
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Find paceite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
