Cuprorivaite is a rare calcium copper silicate known historically as the main component of the synthetic pigment Egyptian Blue. In nature, it occurs as small, vibrant blue platy crystals in thermally metamorphosed limestone blocks found in volcanic ejecta.
Is this cuprorivaite?
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 cuprorivaite with a known reference. Cuprorivaite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cuprorivaite leaves a light blue streak.
- 3Read the lusterHold the specimen under a strong light. Cuprorivaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, deep blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: platy crystals, granular.
Often confused with
Cuprorivaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Cuprorivaite is noticeably harder (Mohs 5 vs. 3.5-4); luster reads vitreous on Cuprorivaite and vitreous to dull on Azurite.
How to tell apart: Streak differs — Cuprorivaite leaves light blue, Turquoise leaves white; luster reads vitreous on Cuprorivaite and waxy on Turquoise.
Often found alongside cuprorivaite
Minerals reported to co-occur with cuprorivaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCuSi₄O₁₀
- Mohs hardness
- 5
- Density
- 3.1 g/cm³
- Streak
- Light Blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Platy Crystals, Granular
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector, Pigment (historical)
- Host rock
- Metamorphosed Limestone Blocks Ejected By Volcanoes
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find cuprorivaite
Classic worldwide localities
- Mount Vesuvius, Italy
- Ettringen, Germany
- Quseir, Egypt
Field-hunting tip
Look in metamorphosed limestone blocks ejected by volcanoes country — that is the host setting where cuprorivaite typically forms. If you start seeing calcite, wollastonite, diopside in float, you are in the right ground. Field specimens usually show a platy crystals, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cuprorivaite on the map
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