Chondrodite, [(Mg, [Fe.sup.2+]).sub.5][(Si[O.sub.4]).sub.2][(F,OH).sub.2], is an uncommon gem material that is known from various localities, including two places in Tanzania: Sumbawanga in the west-central part of the country (Fritz et al., 2007) and Mahenge in south-central Tanzania (Overton, 2011).
Crystal chemistry of titanian
chondrodite and titanian clinohumite of high pressure origin.
For instance, trace amounts of limonite impart a yellowish brown color; serpentine, hornblende, and diopside produce varying tones of green; minute quantities of hematite, vesuvianite, and garnet introduce a reddish brown hue; sphene, epidote, and
chondrodite give a yellow tinge; and plant and animal remains produce shades of dark gray to almost black.
Francois Lietard, Dudley Blauwet and quite a few others had outstanding specimens of the deep reddish brown, translucent to transparent "
chondrodite" crystals which Dudley introduced at the Denver Show of 2005 (see my Denver report in Jan.-Feb.
Dudley Blauwet recently returned from Pakistan with some gemmy red
chondrodite from Ladjur Madea, Kokcha Valley, Badakhshan, Afghanistan.
A small area in one of Dudley's always-intriguing glass cases at the Main Show harbored about a dozen loose, deep brownish red, part-gemmy crystals and tight crystal groups of
chondrodite from a site near Ladjuar Madan, Kokcha Valley, Badakhshan.
Here is a quick survey: Francois Lietard had some brand-new specimens (miniature to cabinet-size) of sharp black spinel octahedrons and spinel-law twins in sizes to 4 cm on edge embedded in white marble, with sharp red-brown opaque
chondrodite crystals to 1.5 cm, from somewhere in Badakhshan, Afghanistan.
for habit-forming behaviors, as the Kristalle booth proudly presented, for instance, four good large cabinet specimens of pyromorphite from the Wheatley mine, Phoenixville, Pennsylvania; about a half-dozen large pieces from the Tilly Foster mine, Brewster, New York, showing deep red-brown
chondrodite crystals to 2.5 cm with clinochlore on massive magnetite; and a few loose gemmy prisms of elbaite whose distinctive, somehow faintly "oily," brownish green color marked them as having come from the old Gillette quarry, Haddam Neck, Connecticut.