Neotocite is an amorphous, manganese-rich silicate mineral that typically forms as a secondary alteration product in manganese deposits. It is easily identified by its dark, often black or brown color and glass-like luster, appearing in massive or botryoidal habit rather than distinct crystals.
Is this neotocite?
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 neotocite with a known reference. Neotocite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark brown to black.
- 3Read the lusterHold the specimen under a strong light. Luster: dull to resinous or vitreous, may be feebly metallic.
- 4Match the color rangeCompare against the expected color range: black, dark brown, liver brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: amorphous, colloform.
Often confused with
Neotocite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Psilomelane is the harder of the two (Mohs 5-6 vs. 3-4); streak differs, so Neotocite leaves dark brown to black, Psilomelane leaves brownish black; luster reads dull to resinous or vitreous, may be feebly metallic on Neotocite and submetallic on Psilomelane.
How to tell apart: Streak differs, so Neotocite leaves dark brown to black, Limonite leaves yellowish-brown; luster reads dull to resinous or vitreous, may be feebly metallic on Neotocite and submetallic to earthy on Limonite.
How to tell apart: Rhodonite is the harder of the two (Mohs 5.5-6.5 vs. 3-4); streak differs, so Neotocite leaves dark brown to black, Rhodonite leaves white; luster reads dull to resinous or vitreous, may be feebly metallic on Neotocite and vitreous, somewhat pearly on cleavages on Rhodonite.
Often found alongside neotocite
Minerals reported to co-occur with neotocite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Mn,Fe)SiO₃·nH₂O
- Mohs hardness
- 3-4
- Density
- 2.8 g/cm³
- Colors
- Streak
- Dark brown to black
- Luster
- Dull to resinous or vitreous, may be feebly metallic
- Transparency
- Opaque, translucent in thin fragments
- Crystal system
- Amorphous
- Crystal habit
- Amorphous, colloform
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- An alteration product of manganese-bearing silicate minerals
Where rockhounds find neotocite
2 mapped spotsClassic worldwide localities
- Aravaipa district, Graham Co., Arizona, USA
- Charles Mountain deposit, Humboldt Co., in the Elsinor area, Riverside Co., and at the Johe Ranch mine, San Louis Obispo Co., California, USA
- Montreal mine, Gogebic Range, Iron Co., Wisconsin, USA
- Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA
- Gestrikland, Sweden
- Långban, Jakobsberg, and the Harstigen mine, near Persberg, Värmland, Sweden
Field-hunting tip
Where it forms: An alteration product of manganese-bearing silicate minerals. If you start seeing rhodonite, calcite, quartz in float, you are in the right ground. Typical habit: amorphous, colloform. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California. Start trip planning there.
Common questions
How do you identify neotocite?+
Where is neotocite found?+
Can I find neotocite in the United States?+
What rocks look like neotocite?+
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Find neotocite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
