Images
Formula: (Pb,Sr)(Y,Mn)Fe3+2(Ti,Fe3+)18O38
Oxide, crichtonite group,
strontium-, yttrium-,
manganese- and titanium- bearing
mineral
Crystal System: Trigonal
Specific gravity: 4.66 calculated
Hardness: 6
Streak: Black
Colour: Black
Weakly RADIOACTIVE
Environments
Metamorphic environments
Hydrothermal environments
Localities
At Mikri Lakka, Eastern Samos, Samos, North Aegean, Greece, gramaccioliite-(Y) occurs as centimetre-sized
crystals in brecciated metamorphosed
bauxite, associated with
diaspore, hematite,
muscovite, chloritoid,
calcite, rutile,
monazite-(Ce), and rare earth element carbonate minerals
bastnäsite-(La) and
parisite-(Ce). Indications are that the coarse-grained vein assemblage
containing gramaccioliite-(Y), diaspore and
chloritoid was succeeded by
calcite, rutile,
monazite-(Ce) and
hematite/limonite. Observations
suggest that gramaccioliite-(Y) was formed at a temperature of about 400°C, under metamorphic conditions.
A high-pressure experiment was conducted to examine the pressure-temperature stability of gramaccioliite-(Y).
Neither phase transformations nor formations of other phases were observed up to 50 kbar, 1100 °C under dry
conditions, indicating that gramaccioliite-(Y) may be stable down the Earth’s mantle
(EJM 22.443-452).
At the type locality, the Sambuco gramaccioliite site, Sambuco, Cuneo Province, Piedmont, Italy,
gramaccioliite-(Y) was found in hydrothermal quartz veins cutting
biotite gneiss as black
lamellar mm-sized crystals. Associated minerals include quartz,
albite, muscovite,
anatase, brookite,
rutile, fluorapatite,
xenotime, pyrite, a mineral of the
synchysite series,
dessauite-(Y) and senaite
(EJM 16.171-175).
Back to Minerals