Muirite is a very rare silicate mineral known almost exclusively from the Big Creek locality in California. It typically occurs as small, glassy, brownish-yellow prismatic crystals or grains associated with other rare barium silicates like sanbornite.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Muirite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this muirite?

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 muirite with a known reference. Muirite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Muirite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Muirite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brown, orange-brown.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: prismatic crystals, anhedral grains.

Often confused with

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

Often found alongside muirite

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

All properties

Chemical formula: Ba₁₀Ca₂MnTiSi₁₂O₃₆(OH)₂Cl₁₀
Mohs hardness: 3.5
Density: 3.08 g/cm³
Colors: Yellow Brown Orange-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Tetragonal
Crystal habit: Prismatic Crystals, Anhedral Grains
Cleavage: Distinct On {001}
Fluorescence: Bright Yellow Under SW UV
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Sanbornite-bearing Rocks
Typical price: $50-500 thumbnail

Where rockhounds find muirite

Classic worldwide localities

Big Creek, Fresno County, California, USA

Field-hunting tip

Look in metamorphosed sanbornite-bearing rocks country — that is the host setting where muirite typically forms. If you start seeing sanbornite, fresnoite, walstromite in float, you are in the right ground. Field specimens usually show a prismatic crystals, anhedral grains habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify muirite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brown, orange-brown.

Where is muirite found?+

Notable localities include Big Creek, Fresno County, California, USA.

How much is muirite 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 muirite?+

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

What minerals are found with muirite?+

Muirite commonly co-occurs with Sanbornite, Fresnoite, Walstromite, Traskite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does muirite form in?+

Muirite typically forms in metamorphosed sanbornite-bearing rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is muirite used for?+

Muirite is used in collector.

Find muirite on the map

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