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.
Is this muirite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch muirite with a known reference. Muirite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale orange.
- 3Read the lusterHold the specimen under a strong light. Luster: subvitreous.
- 4Match the color rangeCompare against the expected color range: orange, brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: anhedral grains.
Often confused with
Muirite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Muirite leaves pale orange, Fresnoite leaves white; luster reads subvitreous on Muirite and vitreous on Fresnoite.
How to tell apart: Walstromite is the harder of the two (Mohs ~3.5 vs. ~2.5); streak differs, so Muirite leaves pale orange, Walstromite leaves white.
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
- Ba₁₀Ca₂MnTiSi₁₀O₃₀(OH,Cl,F)₁₀
- Mohs hardness
- ~2.5
- Density
- 3.86 g/cm³
- Streak
- Pale orange
- Luster
- Subvitreous
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
- Crystal habit
- Anhedral grains
- Cleavage
- Indistinct on {001} and {100}
- Fluorescence
- Bright yellow under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In sanbornite-quartz-bearing metamorphic rock (Fresno Co., California, USA)
Where rockhounds find muirite
Classic worldwide localities
- Big Creek and Rush Creek, Fresno Co., California, USA
- Gunn claim, near Macmillan Pass, Itsy Mountains, Yukon Territory, Canada
Field-hunting tip
Where it forms: In sanbornite-quartz-bearing metamorphic rock (Fresno Co., California, USA). If you start seeing sanbornite, verplanckite, gillespite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify muirite?+
Where is muirite found?+
What rocks look like muirite?+
What minerals are found with muirite?+
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What is muirite used for?+
Find muirite on the map
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