Slawsonite is a rare strontium-bearing feldspar that is primarily valued by mineral collectors for its strong blue fluorescence under short-wave UV light. It is typically found as small, clear to white tabular crystals embedded in metamorphosed limestone or calcium-rich silicate rocks.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareFeldspar Group family

Slawsonite

Hardness: 6
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this slawsonite?

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 slawsonite with a known reference. Slawsonite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Slawsonite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Slawsonite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white, gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often confused with

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

Often found alongside slawsonite

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

All properties

Chemical formula: SrAl₂Si₂O₈
Mohs hardness: 6
Density: 2.79 g/cm³
Colors: Colorless White Gray
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals
Cleavage: Perfect On {001} and {010}
Fluorescence: Strong Blue Under SW UV
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Limestone
Typical price: $50-500 depending on specimen size and clarity

Where rockhounds find slawsonite

Classic worldwide localities

Grenville Province, Ontario, Canada
Khibiny Massif, Russia
Sar-e-Sang, Afghanistan

Field-hunting tip

Look in metamorphosed limestone country, the host setting where slawsonite typically forms. If you start seeing calcite, diopside, grossular in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify slawsonite?+

Mohs hardness is 6. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, gray.

Where is slawsonite found?+

Notable localities include Grenville Province, Ontario, Canada; Khibiny Massif, Russia; Sar-e-Sang, Afghanistan.

How much is slawsonite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen size and clarity. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like slawsonite?+

Slawsonite is most often confused with Anorthite, Albite, Celsian. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with slawsonite?+

Slawsonite commonly co-occurs with Calcite, Diopside, Grossular, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does slawsonite form in?+

Slawsonite typically forms in metamorphosed limestone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is slawsonite used for?+

Slawsonite is used in collector.

Find slawsonite on the map

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