Almarudite is a rare member of the osumilite group, typically found as small, colorless to pale yellow prismatic crystals. It is primarily identified in volcanic rocks and alkaline pegmatites, often occurring in complex mineral assemblages. Due to its extreme rarity and small crystal size, it is a highly sought-after species for mineralogists and specialist collectors.
Is this almarudite?
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 almarudite with a known reference. Almarudite 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. Streak: light orange.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, orange.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: euhedral crystals, tabular.
Often confused with
Almarudite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Almarudite leaves light orange, Osumilite leaves blue-gray.
How to tell apart: Beryl is the harder of the two (Mohs 7.5-8 vs. 6); streak differs, so Almarudite leaves light orange, Beryl leaves white.
How to tell apart: Streak differs, so Almarudite leaves light orange, Milarite leaves white.
Often found alongside almarudite
Minerals reported to co-occur with almarudite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K(□,Na)₂(Mn,Fe,Mg)₂[(Be,Al)₃Si₁₂]O₃₀
- Mohs hardness
- 6
- Density
- 2.72 g/cm³
- Streak
- Light orange
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
- Crystal habit
- Euhedral crystals, tabular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metasomatized silica-rich xenoliths in leucite tephrite lava
Where rockhounds find almarudite
Classic worldwide localities
- A quarry at the Bellerberg volcano lava field, near Ettringen, 2 km north of Mayen, Laacher See region, eastern Eifel area, Germany (type locality)
Field-hunting tip
Where it forms: In metasomatized silica-rich xenoliths in leucite tephrite lava. If you start seeing tridymite, sanidine, quartz in float, you are in the right ground. Typical habit: euhedral crystals, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify almarudite?+
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Find almarudite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
