Penobsquisite is an extremely rare borate mineral discovered in the potash mines of New Brunswick. It typically appears as small, pale yellow, tabular crystals found within evaporite sequences associated with other borate species.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Penobsquisite

Hardness: ~3
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

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Is this penobsquisite?

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 penobsquisite with a known reference. Penobsquisite sits at Mohs ~3, 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: pale yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: euhedral crystals.

Often found alongside penobsquisite

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

All properties

Chemical formula: Ca₂Fe[B₉O₁₃(OH)₆]Cl(H₂O)₂·2H₂O
Mohs hardness: ~3
Density: 2.26 g/cm³
Colors: Pale yellow
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Euhedral crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A very rare residual mineral, obtained by dissolution of halite in a drillcore through a marine evaporite series

Where rockhounds find penobsquisite

Classic worldwide localities

Penobsquis evaporite deposit, near Sussex, New Brunswick, Canada

Field-hunting tip

Where it forms: A very rare residual mineral, obtained by dissolution of halite in a drillcore through a marine evaporite series. If you start seeing halite, sellaite, fluorite in float, you are in the right ground. Typical habit: euhedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify penobsquisite?+

Mohs hardness is ~3. Luster: vitreous. The streak is white. Common colors include pale yellow.

Where is penobsquisite found?+

Notable localities include Penobsquis evaporite deposit, near Sussex, New Brunswick, Canada.

What minerals are found with penobsquisite?+

Penobsquisite commonly co-occurs with Halite, Sellaite, Fluorite, Boracite, Hilgardite, Pringleite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does penobsquisite form in?+

Where it forms: A very rare residual mineral, obtained by dissolution of halite in a drillcore through a marine evaporite series. Working float back to the host body is the standard way to chase a fresh occurrence.

What is penobsquisite used for?+

Penobsquisite is used in collector.

Find penobsquisite on the map

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