Merrillite is a rare phosphate mineral that is primarily known for its presence in extraterrestrial materials, specifically lunar samples and various meteorites. It appears as colorless or white grains and is of immense interest to planetary scientists studying the igneous processes of other celestial bodies.
Is this merrillite?
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 merrillite with a known reference. Merrillite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Merrillite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Merrillite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: anhedral grains.
Often confused with
Merrillite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside merrillite
Minerals reported to co-occur with merrillite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₉NaMg(PO₄)₇
- Mohs hardness
- 5
- Density
- 3.1-3.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Achondrite Meteorites
- Typical price
- very expensive due to scarcity and scientific value
Where rockhounds find merrillite
Classic worldwide localities
- Moon (Lunar samples)
- Martian meteorites
- Angrite meteorites
Field-hunting tip
Look in achondrite meteorites country — that is the host setting where merrillite typically forms. If you start seeing olivine, pyroxene, plagioclase in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find merrillite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
