11) via listric detachment faults, with brittle-ductile transitions on the footwall from
chloritic breccia to semi-ductile mylonite, fanning dips in syn-extensional upper-plate conglomerate units, domino-style upper-plate faults, and consistent angles of 50-70 degrees between detachments and bedding in conglomerate units (Seranne and Seguret 1987; Howard and John 1987; Lister and Davis 1989; Spencer and Reynolds 1989, 1991; Dickinson 1991).
These anomalously older ages maybe related to one or both of: (1) recoil effects due to the presence of K-free
chloritic phases in the altered samples that are synchronous with zeolite formation (Kontak 2000), or (2) incorporation of excess argon during post-eruptive alteration attending zeolite formation.
A 2 X 3 X 4-meter zone in the lower workings has produced the blocky tabular crystals for which the locality is famous, as well as unusual crystals elongated on the a axis, with {001} and {102} termination faces; slender twinned prisms with "feathered" terminations; highly elongated prismatic crystals measuring to 8 cm with "stepped" terminations and associated with chloritic and byssolitic quartz; flattened and slightly curved, smaller crystals nearly identical to those found in Copper Mountain's Jumbo #4 mine; one or two black, nearly opaque, flat, dime-sized, pseudo-hexagonal tablets; and unusual fans and aggregated fans of bi-colored "jackstraw" crystals, some of which penetrate, or are penetrated by, single prismatic crystals and crystal clusters of heavily included quartz.
The intact portion of the pocket--the part we muck out each year--produced slender, prismatic but mostly broken epidote associated with the mountain's largest and perhaps most pleasing green chloritic quartz crystals.
The chemical composition corresponds to the distinction between dominantly talcose and dominantly chloritic ore, and to the amount of barren inclusions (unaltered rock: residual dolomite, pegmatite and mica schist).
Footwall rocks (Cambrian): The footwall consists of pegmatite and calc-silicate gneiss overlain by a few thrust outliers of mica schist or aluminosilicate formations in contact with the chloritic mineralization.
Another scepter quartz, this one from Winterstock, Furka, Switzerland, sits on a
chloritic matrix about 10 X 10 cm; the quartz crystal measures 3 X 10 cm and has a pale purple amethystine head.
The local series is composed of the metamorphic rocks, mostly sericite-phyllites,
chloritic and amphibolitic schists.
The early "feldspar-quartz-mica phase" of Thoreau (1928) cropped out as a
chloritic breccia and enlarged the network of fissures in the Kakontwe.
Andreas also showed me a gorgeous deep yellow-green
chloritic fishtail titanite 5 cm long, which at first I assumed to be from Pakistan or perhaps from some remarkably beneficent Alp, but no, it is so far the only piece taken from a locality to watch for: Gamsberg.