Glaucochroite is a rare calcium-manganese silicate member of the olivine group primarily known from the historic zinc mines of Franklin and Sterling Hill, New Jersey. It typically occurs as prismatic to tabular crystals associated with franklinite and willemite in metamorphosed ore bodies. Collectors look for its characteristic pink to pale brownish hues and its distinct association with other unique zinc-manganese species.
Is this glaucochroite?
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 glaucochroite with a known reference. Glaucochroite sits at Mohs ~6, 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: green, white, pinkish.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: granular.
Often confused with
Glaucochroite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside glaucochroite
Minerals reported to co-occur with glaucochroite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMnSiO₄
- Mohs hardness
- ~6
- Density
- 3.407 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Granular
- Cleavage
- Very poor on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA); in skarn at the contact between diabase and marble (Anakit Creek, Russia); in calc-silicate rocks with manganese ores (Kuruman, South Africa)
Where rockhounds find glaucochroite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
- Anakit Creek, at the mouth of the Lower Tunguska River, central Siberia, Russia
- Wessels mine, near Kuruman, Cape Province, South Africa
- Kombat mine, 49 km south of Tsumeb, Namibia
Field-hunting tip
Where it forms: In a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA); in skarn at the contact between diabase and marble (Anakit Creek, Russia); in calc-silicate rocks with manganese ores (Kuruman, South Africa). If you start seeing nasonite, willemite, andradite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify glaucochroite?+
Where is glaucochroite found?+
What rocks look like glaucochroite?+
What minerals are found with glaucochroite?+
What kind of rock does glaucochroite form in?+
What is glaucochroite used for?+
Find glaucochroite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
