The rock contains aggregates optically resembling whitish scapolite
or marialite, but dravite crystals potentially occurring together with marialite were not found in the material.
He is proud of the miniature to small cabinet-size pieces of typical (for the area) white marble matrix from which rise totally gemmy, pale lavender, well terminated prismatic crystals of scapolite
to 4 cm long, with some of the same matrix pieces also bearing rounded, translucent pine-green diopside crystals, also to 4 cm.
The researchers suggest that one possible source of scapolite
on Mars could have been carbon dioxide combined with calcium plagioclase, probably produced by volcanoes in the ancient Martian past.
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.
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.
The locality is Mpwapwa, Dodoma Province, to which are attributed also those lovely yellow gem scapolite
crystals which we've been seeing around for years.
Meanwhile, in his Mineral Zone warehouse on North Main Street (mentioned earlier), Marcus Origlieri offered about 20 loose, fat, medium-purple, partially gemmy crystals of meionite (the most common of the three members of the scapolite
group), from Badakhshan.
Transparent to milky, prismatic, lustrous scapolite
crystals to more than 2 cm have been found at Alchuri, some in clusters to more than 6 cm.
They occur with clinopyroxene, mica, plagioclase, scapolite
, nepheline and calcite; petrographic studies suggest that these minerals record a diverse, largely retrograde, progression of assemblages.
In that same report, the scapolite
displayed at the Show and shown in Figure 24 is from the Gene and Roz Meieran collection, not the Bill Larson collection.
The Tucson Show of 2004 saw a tentative trickle of lustrous, gemmy, pale purple crystals of scapolite
(to which species of the scapolite
group the material belongs is so far undetermined) from the Kokcha Valley, Badakhshan, Afghanistan; some labels further specify that the locality is near the village of Kiran.