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 — 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 — 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 — that is 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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