3] consists of fragments of molluscan shells and higher amount of calcite rhombohedra.
Some voids are filled with calcite rhombohedra or amorphous forms of CaC[O.
It is found as transparent to translucent and opaque, pale yellow, greenish yellow, amber and brown rhombohedra, 1-2 mm across, sometimes lining cavities, and as botryoidal aggregates, commonly mixed with ankerite and dolomite.
Habit G is characterized by short blocky crystals, 2-5 mm across, with a rhombic cross-section, resembling simple rhombohedra.
One specimen from the Alice mine on the Rainbow vein consists of typical, saddle-shaped rhombohedra overgrown on larger crystals of rhodochrosite (RJ).
The galena is associate d with crystallized black sphalerite, tiny quartz prisms, and a few siderite rhombohedra.
Species Occurrence Barite General occurrence Brochantite Coal Hill vein; oxidation product on chalcopyrite Clinochlore Coal Hill vein; gray-green microcrystals with microcline and pyrite Covellite Locality 9, Redwood; microcrystals resembling iridescent hematite Dolomite Macomb group mines; locality 5; 1-2 mm tan-white rhombohedra
Fluorapatite Coal Hill vein; colorless 0.
This discovery and another large slab [ILLUSTRATION FOR FIGURE 45 OMITTED], with a clustering of five large rhombohedra
, is described and illustrated by Moore (1993).
Crystals form low-angle rhombohedra
that range from less than 1 mm to greater than 5 cm across.
Dolomite occurs as colorless to translucent white rhombohedra
implanted on other minerals.
Ankerite crystals occur as poorly formed rhombohedra
usually having a dull beige or tan color and a chalky appearance.
Dark brown to chocolate-brown rhombohedra
of siderite are relatively common at Onganja, although most specimens consist of crudely intergrown aggregates.