Weathering of carbonate bedrock Crystals freed from carbonate
bedrock now in residual clay.
Crystal from Pakistan. The inclusions are brown in transmitted
light.Crystals sold to me as being from Tibet. Double terminated
crystals are illustrated on the internet from cracks in Septarian
nodules from the French Alps
(http://www.quartzpage.de/dia_text.html), and northern Ohio
(http://www.vasichkominerals.com/Lamereaux1.html). The famous
Herkimer diamonds occur in irregular vugs and cavities within
undeformed Cambrian dolomites in upstate New York. Many images can
be found online, for example
http://www.quartzpage.de/her_text.html. Phases of SiO2, with
typical geothermal gradient ranges. High Pressure phases coesite
and stishovite not shown. Note that increasing pressure is
downQuartz crystal showing typical morphology, and stereo
plot.Index map of known locations with Herkimer type quartz, along
with barite and zinc deposits, andmajor faults. Basemap from the
Geologic Map of Tennessee, 1:250,000, with shaded relief
overlay.*Brief geologic history of East Tennessee, in four
stages.Stratigraphic units of the Valley and Ridge Province of East
Tennessee.Time Line, with age range for crystals relative to
potential open space. Crystals found in the Knox breccias had all
the time from shortly after the formation of the unconformity to
the relatively recent geologic past, while those in the Sevier
Shale and any younger rocks could not have formed in the interval
before the orogeny. There were good images available of karstic
processes and paleokarstic collapse breccias at Zeng, H., Wang, G.,
Janson, X., Loucks, R., Xia, Y., Xu, L., and Yuan, B. (2011).
Characterizing seismic bright spots in deeply buried, Ordovician
Paleokarst strata, Central Tabei uplift, Tarim Basin, Western
China. GEOPHYSICS, 76(4), B127B137
Douglas Dam area at high water.Douglas dam area at mid
water.Mapping features and shoreline on the day I was there.Mapping
features.Interpretative geologic map.Lets go down and look at some
of the geologic outcrops and features.Outcrop with post-Knox
unconformity contact. Lenoir Limestone on top.Unconformable
surface, detail.Fossiliferous Lenoir Limestone just above the
unconformity.Orthocone (Michelinoceras) beds above the Lenoir
Limestone.Sevier Shale along shore farther to the south.Dolomite
veins in brecciated dolomite.Universality of breccias. This one is
on Mars.Outcrop with the pyrobitumen, where I washed it off.Closer
view of pyrobitumen vein.Close up, wet.Dry. You can see the quartz
crystals better.Calcite-filled vugs as a growth medium, a potential
explanation for some of the things we see in these crystals.Closer
view.Large strange chert and calcite nodular feature.Close-up of
massive calcite
