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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 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
- Extraterrestrial bodies
Where rockhounds find merrillite
Classic worldwide localities
- Meteorites (type locality)
Field-hunting tip
Where it forms: Extraterrestrial bodies. If you start seeing olivine, pyroxene, plagioclase 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 merrillite?+
Where is merrillite found?+
What rocks look like merrillite?+
What minerals are found with merrillite?+
What kind of rock does merrillite form in?+
What is merrillite used for?+
Find merrillite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
