(twin) on celestine, Sicily, Italy, no.
A new locality for melanophlogite
, in small, colorless, cubic crystals to about 0.5 mm on matrix, was discovered at Case Montanini, near Parma, Italy.
Melanophlogite Si[O.sub.2] + stabilizing gas molecules
Melanophlogite is a clathrate polymorph of silica stabilized by molecules of gases such as [N.sub.2], C[O.sub.2] and C[H.sub.4] (Nakagawa et al., 2001) trapped within the crystal structure.
Some brown-white color-banded chalcedony has been found in the upper workings, as well as green botryoids with cinnabar inclusions which may be pseudomorphs after melanophlogite. The vein fillings are always small, and display several separate depositional episodes.
Melanophlogite does occur at Clear Creek, a mineral that requires some sort of stabilizing molecules such as C[O.sub.2], [N.sub.2], and C[H.sub.4] for its formation (Nakagawa et al., 2001).
(2002) Pseudomorphic melanophlogites from California.
Melanophlogite, the tetragonal pseudocubic polymorph of Si[O.sub.2], is known from at least five localities within the Franciscan Formation of the Coast Ranges, California.
Melanophlogite (Si[O.sub.2] plus organic compounds) and its chalcedony (quartz) pseudomorphs, have been identified from at least five localities in California, notably within the geologically diverse Franciscan formation of the Mt.
Although melanophlogite is considered to have a cubic structure, studies of material from two localities (Chvaletice, E.
Skinner and Appleman (1963) gave an extensive historical account of melanophlogite research from 1876 through 1891.
The Mount Hamilton locality is about 23 km north of Orestimba Creek and has produced, in addition to chromian alumohydrocalcite, the finest examples of melanophlogite
crystals ever found (Cooper and Dunning, 1972).