It mostly occurs as massive subhedral calcite with some rhombohedron
faces (Figs 6D, E, 7G).
By drawing a dodecahedron and an icosahedron (a regular construct with twenty planes) as duals inside each other he arrived at the acute-angled and obtuse-angled rhombohedrons
which make quasi-periodical spatial filling possible.
There was some surface roughening at the nanometer level of the pyrolyzed surfaces of the control, calcite rhombohedrons
, which again might result from heating the saturated, hydrated layer.
Phantoms are not evident in any crystals, but in some cases the separate rhombohedrons
in parallel alignments differ slightly in color.
Using scanning electron micrographs and aluminum models of calcite rhombohedrons
ectopically grown from hypochlorite-treated foliar chips, he further demonstrated this inclination by the tilted appearance of the crystals and models relative to the foliar surface.
Crystal habits range from elongated hexagonal prisms with low-angle rhombohedron
terminations to prism and scalenohedron combinations in varying proportions.
Collector's Edge was able to deck out its Tucson 2009 showcases with a few hundred beautiful Wudong mine specimens, including cabinet-size plates on which rest calcite-dusted rhombohedrons
of rose-pink rhodochrosite to 4 cm, with small gemmy areas.
3) Formation of tiny sheaf-like sprays of black goethite together with small amethyst crystals--quartz (II)--in "skunk" stripes upon the calcite rhombohedrons
com) had fine specimens at Denver, including one 5-cm matrix piece with perfect, screaming red, twinned rhombohedrons
of cinnabar to 1 cm, for $60.
Forms like the scalenohedron can be generated by stacking tiny rhombohedrons
in a certain way.
Galena forms tiny rounded crystals, and calcite forms gray, distorted rhombohedrons
of saddle-like shape to about 1 mm.
White, gray and pale yellow rhombohedrons
of dolomite are typically the first of the three carbonates to form, being found not only in the massive quartz portion of the vein, but also within the cavity itself.
The deeply colored scalenohedral crystals shown here are quite different from the slightly paler colored rhombohedrons
Pierre Mesage discovered some very fine flattened rhombohedrons
of greenish brown siderite; the specimen quality was better than ever known from this mine.
The distinctive thing is that starry microcrystals of pyrite form perfectly straight bands, some wide, some narrow, along the outside edges of the calcite rhombohedrons
, or following striations across their faces.