Pachnolite is a rare fluoride mineral that typically forms as small, colorless, prismatic crystals in late-stage pegmatites. It is most famously associated with the cryolite deposit at Ivigtut, Greenland, where it often appears as a secondary mineral coating other species.
Is this pachnolite?
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 pachnolite with a known reference. Pachnolite sits at Mohs 3, 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.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, pseudo orthorhombic, twinning common.
Often confused with
Pachnolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pachnolite
Minerals reported to co-occur with pachnolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCaAlF₆·H₂O
- Mohs hardness
- 3
- Density
- 2.965-3.008 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, pseudo orthorhombic, twinning common
- Cleavage
- {001}, good to indistinct
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- As an alteration product of cryolite and other alkali aluminum fluorides, most commonly in pegmatites
Where rockhounds find pachnolite
Classic worldwide localities
- St. Peters Dome, near Pikes Peak, El Paso Co., and in the Goldie carbonatite, McClure Mountain-Iron Mountain, Fremont Co., Colorado, USA
- Zapot pegmatite, 25 km northeast of Hawthorne, Fitting district, Mineral Co., Nevada, USA
- Morefield pegmatite mine, Amelia, Amelia Co., Virginia, USA
- Ivigtut cryolite deposit, southwestern Greenland
- Lake Gjerdingen, Nordmarka, Norway
- Hagendorf pegmatite, Bavaria, Germany
Field-hunting tip
Where it forms: As an alteration product of cryolite and other alkali aluminum fluorides, most commonly in pegmatites. If you start seeing cryolite, thomsenolite, chiolite in float, you are in the right ground. Typical habit: prismatic, pseudo orthorhombic, twinning common. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify pachnolite?+
Where is pachnolite found?+
What rocks look like pachnolite?+
What minerals are found with pachnolite?+
What kind of rock does pachnolite form in?+
What is pachnolite used for?+
Find pachnolite on the map
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