Ungemachite is a rare potassium-sodium-iron sulfate typically found as thin, tabular crystals in arid, oxidized mining environments. It is most recognized for its occurrence in the Chilean nitrate districts, often appearing as small, clear to yellowish hexagonal plates associated with other secondary sulfate minerals.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Ungemachite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this ungemachite?

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 ungemachite with a known reference. Ungemachite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, light yellow.
5
Look at form & habit
Crystal system: trigonal. Typical habit: rhombohedral crystals.

Often confused with

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

mineral

Jarosite

Mohs 2.5-3.5

How to tell apart: Streak differs, so Ungemachite leaves white, Jarosite leaves pale yellow; luster reads vitreous on Ungemachite and subadamantine to vitreous, resinous on fractures on Jarosite.

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Often found alongside ungemachite

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

All properties

Chemical formula: K₃Na₈Fe(SO₄)₆(NO₃)₂·6H₂O
Mohs hardness: 2.5
Density: 2.287 g/cm³
Colors: Colorless Light yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Rhombohedral crystals
Cleavage: On {0001}, perfect
Rarity: Rare
Uses: Collector
Host rock: Rarely formed by the oxidation of pyrite in an arid climate, in veins and cavities in other massive iron sulfates

Where rockhounds find ungemachite

Classic worldwide localities

Chuquicamata, Antofagasta, Chile

Field-hunting tip

Where it forms: Rarely formed by the oxidation of pyrite in an arid climate, in veins and cavities in other massive iron sulfates. If you start seeing clinoungemachite, jarosite, sideronatrite in float, you are in the right ground. Typical habit: rhombohedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ungemachite?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include colorless, light yellow.

Where is ungemachite found?+

Notable localities include Chuquicamata, Antofagasta, Chile.

What rocks look like ungemachite?+

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

What minerals are found with ungemachite?+

Ungemachite commonly co-occurs with Clinoungemachite, Jarosite, Sideronatrite, Metasideronatrite, Metavoltine, Fibroferrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ungemachite form in?+

Where it forms: Rarely formed by the oxidation of pyrite in an arid climate, in veins and cavities in other massive iron sulfates. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ungemachite used for?+

Ungemachite is used in collector.

Find ungemachite on the map

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