Eifelite is an exceptionally rare member of the osumilite group, typically found as microscopic prismatic crystals within volcanic rocks. It is most recognized from its type locality in the Eifel volcanic region of Germany, often occurring alongside sanidine and other volcanic minerals.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareBeryl Group family

Eifelite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this eifelite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch eifelite with a known reference. Eifelite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, light green, light greenish yellow, light yellow.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: prismatic crystals.

Often confused with

Eifelite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Beryl

Mohs 7.5-8

How to tell apart: Beryl is the harder of the two (Mohs 7.5-8 vs. 5-6).

How to tell apart: Streak differs, so Eifelite leaves white, Osumilite leaves blue-gray.

Compare →

Often found alongside eifelite

Minerals reported to co-occur with eifelite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: KNa₂(MgNa)(Mg₃Si₁₂)O₃₀
Mohs hardness: 5-6
Density: 2.67 g/cm³
Colors: Colorless Light greenLight greenish yellowLight yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Prismatic crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In vesicles in contact metamorphosed basement gneiss xenoliths in leucite tephrite

Where rockhounds find eifelite

Classic worldwide localities

Bellerberg volcano, two km north of Mayen, Eifel district, Germany

Field-hunting tip

Where it forms: In vesicles in contact metamorphosed basement gneiss xenoliths in leucite tephrite. If you start seeing tridymite, hematite, pseudobrookite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify eifelite?+

Mohs hardness is 5-6. Luster: vitreous. The streak is white. Common colors include colorless, light green, light greenish yellow, light yellow.

Where is eifelite found?+

Notable localities include Bellerberg volcano, two km north of Mayen, Eifel district, Germany.

What rocks look like eifelite?+

Eifelite is most often confused with Beryl, Osumilite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with eifelite?+

Eifelite commonly co-occurs with Tridymite, Hematite, Pseudobrookite, Pyroxene, Amphibole, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does eifelite form in?+

Where it forms: In vesicles in contact metamorphosed basement gneiss xenoliths in leucite tephrite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is eifelite used for?+

Eifelite is used in collector.

Find eifelite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.