Norrishite is an extremely rare trioctahedral mica found primarily in the manganese mines of the Kalahari Manganese Field. It typically occurs as small, reddish-brown platy crystals associated with various other manganese minerals in high-grade metamorphic environments.
Is this norrishite?
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 norrishite with a known reference. Norrishite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brownish black, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: foliated, massive.
Often confused with
Norrishite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Norrishite leaves light brown, Biotite leaves white; luster reads vitreous on Norrishite and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Streak differs, so Norrishite leaves light brown, Phlogopite leaves white; luster reads vitreous on Norrishite and pearly to submetallic on cleavage on Phlogopite.
Often found alongside norrishite
Minerals reported to co-occur with norrishite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KLiMn₂Si₄O₁₀O₂
- Mohs hardness
- 2.5
- Density
- 3.264 g/cm³
- Colors
- Streak
- Light brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Foliated, massive
- Cleavage
- {001}, perfect; {010} and {100}, poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A major to minor component of manganiferous schists, formed through metamorphism of a stratiform manganese deposit
Where rockhounds find norrishite
Classic worldwide localities
- Hoskins mine, three km west of Grenfell, New South Wales, Australia
Field-hunting tip
Where it forms: A major to minor component of manganiferous schists, formed through metamorphism of a stratiform manganese deposit. If you start seeing manganoan-alkalic amphibole, manganoan-alkalic clinopyroxene, manganoan pectolite-sérandite in float, you are in the right ground. Typical habit: foliated, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify norrishite?+
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What rocks look like norrishite?+
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Find norrishite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
