Originally discovered in lunar samples returned by Apollo 11, Armalcolite is a titanium-rich mineral named after astronauts Armstrong, Aldrin, and Collins. On Earth, it is found primarily in volcanic rocks and kimberlites, typically occurring as microscopic grains associated with ilmenite. It is highly prized by mineral collectors due to its extraterrestrial fame and rarity.
Is this armalcolite?
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 armalcolite with a known reference. Armalcolite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Armalcolite leaves a gray streak.
- 3Read the lusterHold the specimen under a strong light. Armalcolite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: gray, brownish-gray, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: anhedral grains, thin prismatic crystals.
Often confused with
Armalcolite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Armalcolite leaves gray, Manaccanite leaves black; luster reads metallic on Armalcolite and submetallic on Manaccanite.
How to tell apart: Streak differs — Armalcolite leaves gray, Pseudobrookite leaves white; luster reads metallic on Armalcolite and adamantine on Pseudobrookite.
How to tell apart: Streak differs — Armalcolite leaves gray, Iron Ore leaves reddish-brown to black; luster reads metallic on Armalcolite and metallic to submetallic on Iron Ore.
Often found alongside armalcolite
Minerals reported to co-occur with armalcolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mg,Fe²⁺)Ti₂O₅
- Mohs hardness
- 6
- Density
- 4.0-4.1 g/cm³
- Colors
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Anhedral Grains, Thin Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Basaltic Lunar Rocks, Kimberlites, Lamproites
- Typical price
- $50-500 thumbnail
Where rockhounds find armalcolite
Classic worldwide localities
- Moon (Sea of Tranquility)
- USA (Montana)
- South Africa (Karoo Basin)
- Germany (Eifel Mountains)
- Mexico (Durango)
Field-hunting tip
Look in basaltic lunar rocks, kimberlites, lamproites country — that is the host setting where armalcolite typically forms. If you start seeing ilmenite, baddeleyite, chromite in float, you are in the right ground. Field specimens usually show a anhedral grains, thin prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify armalcolite?+
Where is armalcolite found?+
How much is armalcolite worth?+
What rocks look like armalcolite?+
What minerals are found with armalcolite?+
What kind of rock does armalcolite form in?+
What is armalcolite used for?+
Find armalcolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
