Leonardsenite is a rare magnesium fluoride mineral discovered in the Leonard Mine in Butte, Montana. It typically occurs as small, colorless platy crystals associated with quartz and fluorite in mine dump environments.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Leonardsenite

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

Is this leonardsenite?

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 leonardsenite with a known reference. Leonardsenite 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. Leonardsenite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Leonardsenite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals.

Often confused with

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

mineral

Sellaite

Mohs 5

How to tell apart: Sellaite is the harder of the two (Mohs 5 vs. 2).

Often found alongside leonardsenite

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

All properties

Chemical formula: MgF₂
Mohs hardness: 2
Density: 2.16 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Platy Crystals
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins in Mines
Typical price: $50-500 thumbnail

Where rockhounds find leonardsenite

Classic worldwide localities

Leonard Mine, Butte, Montana, USA

Field-hunting tip

Look in hydrothermal veins in mines country — that is the host setting where leonardsenite typically forms. If you start seeing quartz, fluorite in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify leonardsenite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is leonardsenite found?+

Notable localities include Leonard Mine, Butte, Montana, USA.

How much is leonardsenite worth?+

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

What rocks look like leonardsenite?+

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

What minerals are found with leonardsenite?+

Leonardsenite commonly co-occurs with Quartz, Fluorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does leonardsenite form in?+

Leonardsenite typically forms in hydrothermal veins in mines. Working float back to the host body is the standard way to chase a fresh occurrence.

What is leonardsenite used for?+

Leonardsenite is used in collector.

Find leonardsenite on the map

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