Hielscherite is a very rare member of the ettringite group typically found in volcanic xenoliths within the Eifel region of Germany. It commonly forms delicate, needle-like hexagonal prisms that can be difficult to distinguish from ettringite without chemical analysis. Collectors prize it primarily for its extreme rarity and unique geological occurrence.
Is this hielscherite?
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 hielscherite with a known reference. Hielscherite sits at Mohs 2-2.5, 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; silky aggregates.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: acicular to prismatic crystals.
Often confused with
Hielscherite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hielscherite
Minerals reported to co-occur with hielscherite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Si(SO₄)(SO₃)(OH)₆·11H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.82 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous; silky aggregates
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Acicular to prismatic crystals
- Cleavage
- Distinct on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities in alkaline basalt or also in xenoliths in volcanic glass
Where rockhounds find hielscherite
Classic worldwide localities
- Graulay quarry near Hillesheim, western Eifel Mountains, Rhineland-Palatinate, Germany
Field-hunting tip
Where it forms: In miarolitic cavities in alkaline basalt or also in xenoliths in volcanic glass. If you start seeing diopside, nepheline, fluorapatite in float, you are in the right ground. Typical habit: acicular to prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hielscherite?+
Where is hielscherite found?+
What rocks look like hielscherite?+
What minerals are found with hielscherite?+
What kind of rock does hielscherite form in?+
What is hielscherite used for?+
Find hielscherite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
