Gadolinite-(Y)
Mineral Y2FeBe2Si2O10
Also called Gadolinite
Take care.
- Radioactive: Keep it in a closed, labelled box away from where people sit or sleep, handle it briefly, wash your hands after, and never grind or cut it.
About it
Black, glassy masses and crude crystals in granite pegmatites, often metamict and weakly radioactive from thorium and uranium; Ytterby, Sweden, where several rare earths were found.
- Type
- Mineral
- Group
- Silicate (nesosilicate), gadolinite group
- Formula
- Y2FeBe2Si2O10
- Hardness (Mohs)
- 6.5–7
- Specific gravity
- 4–4.5
- Streak
- greenish grey
- Lustre
- vitreous (glassy), greasy
- Crystal system
- Monoclinic
- Colours
- black, greenish black, brown, green
- Transparency
- transparent, translucent, opaque
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.