Ferriandrosite-(La) is a rare member of the allanite group, typically occurring as dark, submetallic prismatic crystals. It is primarily found in hydrothermal veins associated with metamorphic or volcanic processes, making it a prized species for advanced systematic mineral collectors.
Is this ferriandrosite-(la)?
4-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 ferriandrosite-(la) with a known reference. Ferriandrosite-(La) sits at Mohs 6-6.5, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 3Match the color rangeCompare against the expected color range: dark brown.
- 4Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, elongated crystals.
Often confused with
Ferriandrosite-(La) vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ferriandrosite-(la)
Minerals reported to co-occur with ferriandrosite-(la). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺La³⁺Fe³⁺AlMn²⁺(Si₂O₇)(SiO₄)O(OH)
- Mohs hardness
- 6-6.5
- Density
- 4.23 g/cm³
- Colors
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, elongated crystals
- Cleavage
- Imperfect on {001}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In tephroite-calcite veinlets cutting a stratiform ferromanganese deposit
Where rockhounds find ferriandrosite-(la)
Classic worldwide localities
- Shobu area, Ise City, Mie Prefecture, Japan
Field-hunting tip
Where it forms: In tephroite-calcite veinlets cutting a stratiform ferromanganese deposit. If you start seeing ferriakasakaite-, rhodochrosite, bementite in float, you are in the right ground. Typical habit: prismatic, elongated crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferriandrosite-(la)?+
Where is ferriandrosite-(la) found?+
What rocks look like ferriandrosite-(la)?+
What minerals are found with ferriandrosite-(la)?+
What kind of rock does ferriandrosite-(la) form in?+
What is ferriandrosite-(la) used for?+
Find ferriandrosite-(la) on the map
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