Gramaccioliite-(Y) is a rare mineral belonging to the crichtonite group, typically occurring as small, dark, rhombohedral crystals in pegmatite cavities. It is distinguished by its yttrium content and is usually found in highly specialized geological settings like the famous Baveno granite.
Is this gramaccioliite-(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 gramaccioliite-(y) with a known reference. Gramaccioliite-(Y) sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: hexagonal, tabular.
Often confused with
Gramaccioliite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Gramaccioliite-(Y) leaves black, Crichtonite leaves dark gray.
How to tell apart: Streak differs, so Gramaccioliite-(Y) leaves black, Davidite-(La) leaves grayish black to dark brown; luster reads metallic on Gramaccioliite-(Y) and vitreous to submetallic, shining on Davidite-(La).
Often found alongside gramaccioliite-(y)
Minerals reported to co-occur with gramaccioliite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Pb,Sr)(Y,Mn)Fe³⁺₂(Ti,Fe³⁺)₁₈O₃₈
- Mohs hardness
- 5-6
- Density
- 4.66 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Hexagonal, tabular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In hydrothermal quartz veins cutting biotite gneiss (Italy); in metamorphosed bodies of brecciated bauxite and marble (Greece)
Where rockhounds find gramaccioliite-(y)
Classic worldwide localities
- Sambuco di Vinadio, Stura Valley, Piedmont, Italy and from Mikri Lakka, eastern coast of Samos Island, Greece
Field-hunting tip
Where it forms: In hydrothermal quartz veins cutting biotite gneiss (Italy); in metamorphosed bodies of brecciated bauxite and marble (Greece). If you start seeing quartz, albite, muscovite in float, you are in the right ground. Typical habit: hexagonal, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gramaccioliite-(y)?+
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Is gramaccioliite-(y) safe to handle?+
What rocks look like gramaccioliite-(y)?+
What minerals are found with gramaccioliite-(y)?+
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Find gramaccioliite-(y) on the map
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