Isselite is a rare iron sulfate mineral that forms as an oxidation product of sulfide minerals. It typically appears as delicate, pearly platy crystals or crusts and is highly sensitive to humidity, requiring dry storage conditions to prevent dehydration.

Hardness

2.5

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrarenull family

Isselite

Hardness: 2.5
Luster: Pearly
Streak: White
Transparency: Translucent

Is this isselite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch isselite with a known reference. Isselite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Isselite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Isselite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, yellowish-white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals, crusts.

Often confused with

Isselite vs. its common look-alikes — and how to tell them apart in the field.

mineral

Coquimbite

Mohs 2.5

How to tell apart: Luster reads pearly on Isselite and vitreous on Coquimbite.

How to tell apart: Luster reads pearly on Isselite and silky on Fibroferrite.

Compare →

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: Fe₂³⁺(SO₄)₃·10H₂O
Mohs hardness: 2.5
Density: 2.12 g/cm³
Colors: White Yellowish-white
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy Crystals, Crusts
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Oxidized Ore Deposits
Typical price: $50-300 per specimen

Where rockhounds find isselite

Classic worldwide localities

Issel, France
Cerro Pintado, Chile

Field-hunting tip

Look in oxidized ore deposits country — that is 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?+

Mohs hardness is 2.5. It typically shows a pearly luster. The streak is white. Common colors include white, yellowish-white.

Where is isselite found?+

Notable localities include Issel, France; Cerro Pintado, Chile.

How much is isselite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like isselite?+

Isselite is most often confused with Coquimbite, Fibroferrite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with isselite?+

Isselite commonly co-occurs with Jarosite, Melanterite, Copiapite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does isselite form in?+

Isselite typically forms in oxidized ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is isselite used for?+

Isselite is used in collector.

Find isselite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.