SERPENTINITES
ÒGreen marbleÓ is often available from granite &
marble companies. However, the actual material is not even close to what
the term Ògreen marbleÓ implies or suggests. ÒGreen marbleÓ is actually serpentinite,
which results from the metamorphism of olivine-rich ultramafic igneous rocks (peridotites).
Serpentinites
are principally composed of serpentine, although small amounts of magnetite are
often present.
ÒGreen MarbleÓ - serpentinite (undetermined
commercial name; undetermined provenance).
Verde Mare Marble - serpentinite from the Italian Alps. Minerals reported from this unit include
antigorite serpentine, forsterite olivine, diopside pyroxene + accessory
chlorite, titanian magnetite, and local chrysotile asbestos.
Geologic Unit & Age & Alteration History: Malenco Serpentinite (a.k.a. Malenco
Peridotite; Val Malenco Peridotite; Malenco Ultramafics; Malenco Ophiolite) -
largely serpentinized subcontinental mantle of Permian age, uplifted to
seafloor exposure in the Jurassic, deformed as an ultrmafic nappe metamorphosed
to epidote-amphibolite grade during the Alpine Orogeny in the
Oligocene-Miocene.
Locality:
commercial quarry near town of Val Malenco, Lombardy Region, Raethian Alps
(east-central Alps), near border with Switzerland, far-northern Italy.