Lourenswalsite is a rare potassium-barium niobium silicate mineral typically occurring as soft, pearly, micaceous flakes. It is most famous for its occurrences within the alkaline igneous rocks of the Magnet Cove complex in Arkansas. Collectors look for its distinctive platy habit and white color when inspecting microspecimens from rare-earth-bearing pegmatites.
Is this lourenswalsite?
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 lourenswalsite with a known reference. Lourenswalsite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to dull.
- 4Match the color rangeCompare against the expected color range: brownish gray, pearl gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: pseudo hexagonal, rosette.
Often confused with
Lourenswalsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Lourenswalsite leaves gray white, Biotite leaves white; luster reads pearly to dull on Lourenswalsite and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Streak differs, so Lourenswalsite leaves gray white, Phlogopite leaves white.
How to tell apart: Streak differs, so Lourenswalsite leaves gray white, Muscovite leaves white; luster reads pearly to dull on Lourenswalsite and vitreous to pearly or silky on Muscovite.
Often found alongside lourenswalsite
Minerals reported to co-occur with lourenswalsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Ba)₂Ti₄(Si,Al)₆O₁₄(OH)₁₂
- Mohs hardness
- 2
- Density
- 3.17 g/cm³
- Colors
- Brownish grayPearl gray
- Streak
- Gray white
- Luster
- Pearly to dull
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Pseudo hexagonal, rosette
- Cleavage
- {001}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed during weathering, in vugs and miarolitic cavities in a titaniferous nepheline syenite
Where rockhounds find lourenswalsite
Classic worldwide localities
- Diamond Jo quarry, Magnet Cove, Hot Spring Co., Arkansas, USA
Field-hunting tip
Where it forms: A secondary mineral formed during weathering, in vugs and miarolitic cavities in a titaniferous nepheline syenite. If you start seeing labuntsovite, delindeite, pectolite in float, you are in the right ground. Typical habit: pseudo hexagonal, rosette. Train your eye for that shape before scanning the outcrop.
Common questions
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What rocks look like lourenswalsite?+
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Find lourenswalsite on the map
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