Kremersite is a rare ammonium iron chloride mineral typically found as a volcanic sublimate in active fumaroles. It forms bright red octahedral crystals or crusts that are highly sensitive to moisture and must be stored in a dry, sealed environment to prevent decomposition.

Hardness

Mohs

Luster

Vitreous

Streak

Yellowish

Transparency

Transparent

mineralrare

Kremersite

Hardness: 2
Luster: Vitreous
Streak: Yellowish
Transparency: Transparent

Is this kremersite?

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 kremersite with a known reference. Kremersite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kremersite leaves a yellowish streak.
3
Read the luster
Hold the specimen under a strong light. Kremersite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: red, reddish-orange.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral crystals, crusts.

Often confused with

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

mineral

Erythrosiderite

Mohs 2.5

How to tell apart: Streak differs — Kremersite leaves yellowish, Erythrosiderite leaves yellowish-orange.

Compare →

Often found alongside kremersite

Minerals reported to co-occur with kremersite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (NH₄,K)₂FeCl₅·H₂O
Mohs hardness: 2
Density: 2.28 g/cm³
Colors: Red Reddish-orange
Streak: Yellowish
Luster: Vitreous
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Octahedral Crystals, Crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Fumaroles
Typical price: $50-300 per specimen

Where rockhounds find kremersite

Classic worldwide localities

Vesuvius, Italy
Etna, Italy
Tolbachik, Russia

Field-hunting tip

Look in fumaroles country — that is the host setting where kremersite typically forms. If you start seeing halite, sylvite, cotunnite in float, you are in the right ground. Field specimens usually show a octahedral crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kremersite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is yellowish. Common colors include red, reddish-orange.

Where is kremersite found?+

Notable localities include Vesuvius, Italy; Etna, Italy; Tolbachik, Russia.

How much is kremersite 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.

Is kremersite safe to handle?+

It contains toxic constituents. Contains chlorides and ammonium; handle with care as it is soluble and may be toxic if ingested or inhaled in dust form. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like kremersite?+

Kremersite is most often confused with Erythrosiderite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with kremersite?+

Kremersite commonly co-occurs with Halite, Sylvite, Cotunnite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kremersite form in?+

Kremersite typically forms in fumaroles. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kremersite used for?+

Kremersite is used in collector.

Find kremersite on the map

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