Perettiite-(Y) is an exceptionally rare yttrium manganese borosilicate mineral known primarily from alkaline pegmatites in the Zomba District of Malawi. It typically occurs as small, dark prismatic crystals embedded in matrix. Due to its rarity, it is highly sought after by advanced systematic mineral collectors.
Is this perettiite-(y)?
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 perettiite-(y) with a known reference. Perettiite-(Y) sits at Mohs ~7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: colorless.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals.
Often confused with
Perettiite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Perettiite-(Y) leaves colorless, Gadolinite-(Y) leaves greenish gray.
How to tell apart: Perettiite-(Y) is noticeably harder (Mohs ~7 vs. 5.5-6); streak differs, so Perettiite-(Y) leaves colorless, Allanite leaves gray; luster reads vitreous on Perettiite-(Y) and submetallic on Allanite.
Often found alongside perettiite-(y)
Minerals reported to co-occur with perettiite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Y₂Mn₄FeSi₂B₈O₂₄
- Mohs hardness
- ~7
- Density
- 4.533 g/cm³
- Colors
- Streak
- Colorless
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic crystals
- Cleavage
- Good on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As inclusions in gemmy phenakite crystals from pockets in granitic pegmatite
Where rockhounds find perettiite-(y)
Classic worldwide localities
- Khetchel, Molo area, Momeik, north of Mogok, Myanmar
Field-hunting tip
Where it forms: As inclusions in gemmy phenakite crystals from pockets in granitic pegmatite. If you start seeing schorl, tusionite, columbite- in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify perettiite-(y)?+
Where is perettiite-(y) found?+
What rocks look like perettiite-(y)?+
What minerals are found with perettiite-(y)?+
What kind of rock does perettiite-(y) form in?+
What is perettiite-(y) used for?+
Find perettiite-(y) on the map
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