Although oriented toward mineral collectors, some items of interest to gemmologists that appeared in 2014 include tourmaline from Brazil, Tanzania and Nepal; gem-quality wurtzite and colour-change axinite-(Mg) from Merelani, Tanzania; demantoid from Iran; benitoite from California; and daylight-luminescent hyalite
opal from Mexico (as reported in this issue of The Journal).
These mineral species described are: Hornblende, Epidote, Piemontite, Chabazite, Prehnite, Pyrite, Chalcopyrite, Clinozoisite, Dravite var Tourmaline, Chlorite, Garnet var Almandine, Sulphur (as free crystals), Calcite, Kaolinite, Hyalite
Such is the case with the daylight-fluorescing, vivid green transparent hyalite
that was recently unearthed in Zacatecas, Mexico (Fritsch et al., 2014; see Figure 1 and the cover of this issue).
Thus it's helpful that midway through this work we come on "An Opal Glossary of Terms," compiled by Si and Ann Frazier, to which we can turn when other chapters invoke terms like Ariki, black nobby, cacholong, conk, girasol, hyalite
, Newton's rings, tabasheer, Yowah nut, and many others just as peculiar.
For several weeks thereafter, more aquamarine was collected; some of the crystals are associated with schorl, fluorescent lime-green hyalite
and complexly twinned orthoclase crystals displaying Carlsbad, Baveno and Manebach twins.
Some surfaces show iron-oxide staining, and commonly there are adhering patches of warty white hyalite
. In the same tent, Herb Kaiser showed me a nice selection of specimens of the now well known green andradite ("demantoid") crystals found embedded in chowdery quartz/feldspar/calcite matrix near Usakos, Namibia: the lustrous, part-gemmy, brownish green dodecahedral crystals in this lot reach 2 cm.
A very rare and unusual variety of fluorite consists of tiny, vitreous, colorless spheroids, forming botryoidal crusts reminiscent of hyalite
Other, less common mineral species that have been reported from the Klein Spitzkoppe occurrences include bixbyite, chabazite, columbite, euxenite-(Y), gibbsite, nacrite, opal (hyalite
), pyrophyllite, talc, ferberite and zircon.
In the Zenobia mine, opal was locally an abundant last-phase primary vein mineral reported in vugs to great depth, as yellow masses of tangled wires and rods and as hyalite
(Lindgren and Ransome, 1906).
Associated minerals are: kozoite-(Nd), lanthanite-(Nd), kimuraite-(Y), lokkaite-(Y), calcite, aragonite and opal (variety, hyalite
The matrix rock for the sulfur crystals is highly-altered volcanic material consisting now mainly of clay minerals, opal (hyalite
), alunite, gypsum and minor films of manganese oxides.