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There are Orbicular jaspers from a number of locations
within the Franciscan Formation, from as far north as the Washington state
coast, called olympic jasper, and it shows up occasionally. There are several
varieties of orbicular that seem to originate from Snow Mountain, up near
Stonyford California. Robyn's Poppy is one of these, a variety that I discovered
a few years ago, on the next mountain to the east. Then there is Snow Mountain
Poppy, that turns up occasionally in the alluvial fans of Snow Mountain, mostly
found occasionally in Stony Creek. Another yellow type orbicular goes by the
name of Eel River Orbicular, however The Eel River has it's headwaters up in the
Yolo Bollie Mountains which happen to be in the northwestern alluvial drainage
of Snow Mountain complex. Pope Valley over in Napa County could also be an
ancient drainage from Snow mountain, but off towards the southwest.
When they were digging down to bedrock to put in the footing for the Golden Gate
Bridge on the San Francisco shore, they began to dredge up an orbicular Jasper
there, down near the bedrock. The Golden Gate Poppy specimens are mostly locked
away in safes now, and are considered treasures, by the few lucky owners. I've
seen only 1 piece of that in 35 years of collecting.
I have found some examples of tiny colorful orbicular jaspers near Hearst
Castle, but I would assume that could have come out of any ocean drainage to the
north of San Simeon Beach. Maybe a relative to the Golden Gate Orbicular..., but
it should be mentioned that San Simeon beach is actually part of the Pacific
Plate, and the border with the franciscan formation is some 25 miles inland,
nearer to Parkfield, Cal.
The origin of, and nature of orbicular jaspers within the Franciscan Formation
is still a source of considerable debate and contention, But nobody would deny
that the Franciscan has more than it's fair share of orbicular jaspers.
It's been brought up and discussed vigorously, that long ago, when Madagascar
and California were both part of the supercontinent Pangea; that they were
equidistant from the equator, but on opposite sides, and that they shared much
geology and climate similarities, including a massive fault-line structure. The
west coast of Madagascar actually ripped away from the ancient continent, and it
is that precise coastline that produces the Ocean Jasper. I think that the
faultline structure, and the plate tectonics dynamics had something to do with
the formation of the orbs.
Thomas Clark - Author
Map and webpage design - Neil Yeager