The rock contains aggregates optically resembling whitish scapolite
or marialite, but dravite crystals potentially occurring together with marialite were not found in the material.
However, a number of papers have solved various aspects of the metasomatic processes including widespread formation of scapolite
metagabbro [19-21, 27] through Mg-Cl metasomatism, replacement textures in apatite [28-30], rutile formation , carbonate deposition , tourmaline formation , and sapphirine-corundum crystallization .
Milisenda (German Gemmological Association, IdarOberstein) and co-authors examined some gemstones with photochromism: hackmanite, tugtupite and scapolite
. The interesting colour behaviour of these gems is due to S- ions.
Somewhere near Karur, Tamil Nadu State, southern India, at least three impressive specimens of scapolite
have recently come to light.
Pseudomorphs of muscovite: Gigantolite (after cordierite), Cataspilite (after cordierite), Pinite (after cordierite); Oncophyllite (after feldspars), Pinitoide (after feldspars); Gieseckite (after nepheline), Liebenerite (after nepheline); Gilbertite (after topas); Killinite (after spodumen); Terenite (after scapolite
), Wilsonite (after scapolite
A combination of well-characterized minerals and synthetic materials were used to calibrate for EPMA, including SMS scapolite
(S and Cl), Corning W glass (6) (Co), SMS gahnite (Zn), SMS cassiterite (Sn), SMS strontianite and Corning X glass (Sr).
, it is somewhat rare on Earth, where it usually forms by heat-processing of carbonate rocks, often at points of contact with volcanic rocks.
Diamond-bearing eclogite xenoliths * Cat's-eye calcite from Pakistan * Large chatoyant Brazilian emerald * Nonbeadcultured pearls from Strombus gigas * Purple scapolite
* Synthetic star sapphire with diffusion-induced colour and star * Partially filled blue chalcedony * Presumably oiled ruby * Inclusions in synthetic star sapphire * Diamond slices * Large Namibian demantoid * Nephrite from British Columbia * Baroque cultured pearls * Ruby from Namya, Myanmar * Rock Creek sapphire update * Unusual tourmaline necklace * Conference reports.
Other gem mineral deposits include the Mpwapwa district in the Dodoma region (for yellow scapolite
crystals), Babati in the Manyara region (dichroic cordierite), the Sumbawanga and Lake Manyara deposits (emerald and alexandrite), the sapphire, tourmaline and alexandrite deposits of Songea and Tunduru in the Ruvuma region, the Williamson (Mwadui) diamond deposit (the world's largest exploitable kimberlite pipe) in the Tabora region, the Umba River deposit in the Tanga region (sapphire, "umbalite" variety of almandine, and chromium-rich elbaite), Sangasanga in the Morogoro region (liddicoatite and rossmanite), and the Ipanko mines near Mahenge (big red spinel crystals)-among others.
Formation of inorganic, non-volatile chlorine compounds such as NaCl, KCl, Ca[Cl.sub.2], complex silicates and alumino-silicates like sodalite [Na.sub.8][[(AlSi[O.sub.4]).sub.6][Cl.sub.2]] or scapolite
[(Na,Ca).sub.4][[Al.sub.3][(Si,Al).sub.3][Si.sub.6][O.sub.24](Cl,C[O.sub.3])] is of decisive importance.
Tucson 2015: exceptional colored stones and gem artistry, Brazilian Cu-bearing tourmaline and emerald, Oregon sunstone and pearl market updates * Conference reports * Amblygonitemontebrasite carving * Moroccan amethyst * Dumortierite in quartz * Jadeite with high albite content * Moldavite imitation * Iridescent scapolite
* Composite quartz beads * CVD synthetic diamond with unstable color * The Foldscope.
Beds of massive, coarse-grained crystalline limestone, commonly dolomitic and siliceous, are prominent; MacFarlane (1975) found ubiquitous dispersed flakes of phlogopite and graphite in the limestone, along with lesser amounts of apatite, scapolite
, tremolite, diopside, forsterite, hornblende and garnet.