Marshite is a rare copper iodide mineral that typically occurs as small, sharp, red-to-brown tetrahedral crystals. It is best known by collectors for its striking red fluorescence under ultraviolet light. It is almost exclusively found in the supergene oxidized zones of specific copper-rich ore deposits.
Is this marshite?
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 marshite with a known reference. Marshite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Marshite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Marshite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: red, brownish-red, colorless.
- 5Look at form & habitCrystal system: cubic. Typical habit: tetrahedral crystals.
Often confused with
Marshite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Marshite leaves white, Native Copper leaves copper-red; luster reads adamantine on Marshite and metallic on Native Copper.
How to tell apart: Marshite is noticeably harder (Mohs 2.5 vs. 1.5); streak differs, so Marshite leaves white, Iodargyrite leaves yellow; luster reads adamantine on Marshite and resinous on Iodargyrite.
Often found alongside marshite
Minerals reported to co-occur with marshite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuI
- Mohs hardness
- 2.5
- Density
- 5.92 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Tetrahedral Crystals
- Cleavage
- Distinct On {111}
- Fluorescence
- Bright Red Under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper Ore Deposits
- Typical price
- $50-500 depending on specimen size and quality
Where rockhounds find marshite
Classic worldwide localities
- Broken Hill, Australia
- Chuquicamata, Chile
- Tsumeb, Namibia
Field-hunting tip
Look in oxidized zones of copper ore deposits country, the host setting where marshite typically forms. If you start seeing cuprite, iodargyrite, cerussite in float, you are in the right ground. Field specimens usually show a tetrahedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find marshite on the map
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