Isselite is a rare copper sulfate, typically blue. It is a late-stage, secondary phase in a Fe-Ni-Co sulfide deposit. It was first described from Lagoscuro mine, Ceranesi, Genoa Province, Liguria, Italy.
Is this isselite?
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 isselite with a known reference. Isselite 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. Isselite leaves a light blue streak.
- 3Read the lusterHold the specimen under a strong light. Isselite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, crusts.
Often confused with
Isselite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Isselite leaves light blue, Coquimbite leaves white.
How to tell apart: Streak differs, so Isselite leaves light blue, Fibroferrite leaves white; luster reads vitreous on Isselite and silky on Fibroferrite.
Often found alongside isselite
Minerals reported to co-occur with isselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₆(SO₄)(OH)₁₀(H₂O)₄·H₂O
- Mohs hardness
- 2.5
- Density
- 3.00 g/cm³
- Colors
- Streak
- Light Blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Crusts
- Cleavage
- Good On {001} and {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Ore Deposits
Where rockhounds find isselite
Classic worldwide localities
- Lagoscuro mine, Liguria, Italy
Field-hunting tip
Look in oxidized ore deposits country, the host setting where isselite typically forms. If you start seeing jarosite, melanterite, copiapite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify isselite?+
Where is isselite found?+
What rocks look like isselite?+
What minerals are found with isselite?+
What kind of rock does isselite form in?+
What is isselite used for?+
Find isselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
