Pertlikite is a very rare member of the garnet group specifically occurring as a secondary mineral in volcanic cavities. Collectors typically find it as small, yellowish-dark olive-green to black dodecahedral crystals associated with quartz and calcite within basaltic host rocks.

Hardness

7-7.5

Mohs

Streak

Grayish green

Transparency

Translucent

mineralrareGarnet Group family

Pertlikite

Hardness: 7-7.5
Streak: Grayish green
Transparency: Translucent

No image

Is this pertlikite?

4-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 pertlikite with a known reference. Pertlikite sits at Mohs 7-7.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: grayish green.
3
Match the color range
Compare against the expected color range: dark olive green, black.
4
Look at form & habit
Crystal system: tetragonal. Typical habit: granular.

Often confused with

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

mineral

Grossular

Mohs 6.5-7

How to tell apart: Streak differs, so Pertlikite leaves grayish green, Grossular leaves white.

How to tell apart: Streak differs, so Pertlikite leaves grayish green, Andradite leaves white.

Compare →

Often found alongside pertlikite

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

All properties

Chemical formula: K₂(Fe²⁺,Mg)₂(Mg,Fe³⁺)₄Fe³⁺₂Al(SO₄)₁₂·18H₂O
Mohs hardness: 7-7.5
Density: 2.59 g/cm³
Colors: Dark olive green Black
Streak: Grayish green
Transparency: Translucent
Crystal system: Tetragonal
Crystal habit: Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a pyrite-bearing trachytic eruptive rock, and probably formed after the oxidation of pyrite

Where rockhounds find pertlikite

Classic worldwide localities

Madeni Zakh, Iran

Field-hunting tip

Where it forms: In a pyrite-bearing trachytic eruptive rock, and probably formed after the oxidation of pyrite. If you start seeing metavoltine, botryogen, pyrite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pertlikite?+

Mohs hardness is 7-7.5. The streak is grayish green. Common colors include dark olive green, black.

Where is pertlikite found?+

Notable localities include Madeni Zakh, Iran.

What rocks look like pertlikite?+

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

What minerals are found with pertlikite?+

Pertlikite commonly co-occurs with Metavoltine, Botryogen, Pyrite, Alunite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pertlikite form in?+

Where it forms: In a pyrite-bearing trachytic eruptive rock, and probably formed after the oxidation of pyrite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pertlikite used for?+

Pertlikite is used in collector.

Find pertlikite on the map

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