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. Streak: bright to pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: brown, colorless, light yellow, dark brownish red.
- 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: Cuprite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs, so Marshite leaves bright to pale yellow, Cuprite leaves brownish red, shining.
How to tell apart: Marshite is noticeably harder (Mohs 2.5 vs. 1.5); streak differs, so Marshite leaves bright to pale yellow, Iodargyrite leaves yellow, shining; luster reads adamantine on Marshite and resinous to adamantine, pearly on cleavage surfaces 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
- 5.59-5.68 g/cm³
- Colors
- Streak
- Bright to pale yellow
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Tetrahedral crystals
- Cleavage
- {011}, perfect
- Fluorescence
- Dark red under LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in the oxidized zone of a metamorphosed Pb–Zn–Ag deposit (Broken Hill, Australia); in the oxidized zone of a porphyry copper deposit (Chuquicamata, Chile)
Where rockhounds find marshite
Classic worldwide localities
- Broken Hill, New South Wales, and in the Poona mine, 5 km northeast of Moonta, South Australia
- Chuquicamata, Antofagasta, Chile
- Löytösuo area, Ylikiiminki, Finland
Field-hunting tip
Where it forms: A rare mineral in the oxidized zone of a metamorphosed Pb–Zn–Ag deposit (Broken Hill, Australia); in the oxidized zone of a porphyry copper deposit (Chuquicamata, Chile). If you start seeing copper, cuprite, cerussite in float, you are in the right ground. Typical habit: tetrahedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify marshite?+
Where is marshite found?+
Is marshite safe to handle?+
What rocks look like marshite?+
What minerals are found with marshite?+
What kind of rock does marshite form in?+
What is marshite used for?+
Find marshite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
