Aspidolite is a rare sodium-dominant member of the trioctahedral mica group, chemically analogous to phlogopite. It typically occurs as small, transparent, platy crystals in metamorphosed dolomitic marbles, often difficult to distinguish from common phlogopite without chemical analysis.

Hardness

2.5

Mohs

Luster

Pearly

Streak

White

Transparency

Transparent

mineralrareMica Group family

Aspidolite

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

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Is this aspidolite?

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 aspidolite with a known reference. Aspidolite 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. Aspidolite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Aspidolite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: colorless, pale yellow, brown, greenish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy, micaceous, tabular crystals.

Often confused with

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

Often found alongside aspidolite

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

All properties

Chemical formula: NaMg₃(AlSi₃O₁₀)(OH)₂
Mohs hardness: 2.5
Density: 2.9-3.0 g/cm³
Colors: Colorless Pale Yellow Brown Greenish
Streak: White
Luster: Pearly
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Platy, Micaceous, Tabular Crystals
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Metamorphosed Dolomite Rocks
Typical price: $20-150 thumbnail to miniature

Where rockhounds find aspidolite

Classic worldwide localities

Ticino, Switzerland
Val Malenco, Italy
Khibiny Massif, Russia

Field-hunting tip

Look in metamorphosed dolomite rocks country — that is the host setting where aspidolite typically forms. If you start seeing tremolite, diopside, calcite in float, you are in the right ground. Field specimens usually show a platy, micaceous, tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify aspidolite?+

Mohs hardness is 2.5. It typically shows a pearly luster. The streak is white. Common colors include colorless, pale yellow, brown, greenish.

Where is aspidolite found?+

Notable localities include Ticino, Switzerland; Val Malenco, Italy; Khibiny Massif, Russia.

How much is aspidolite worth?+

Typical asking prices fall in the range of $20-150 thumbnail to miniature. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like aspidolite?+

Aspidolite is most often confused with Phlogopite, Biotite, Muscovite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with aspidolite?+

Aspidolite commonly co-occurs with Tremolite, Diopside, Calcite, Dolomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does aspidolite form in?+

Aspidolite typically forms in metamorphosed dolomite rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is aspidolite used for?+

Aspidolite is used in collector, scientific research.

Find aspidolite on the map

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