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Glendonites found in Alaska are rare compared to |
other
glendonite types -- they are stellate, globular,
yet with wide, broad blades. Their color appears whitish but that could
be a coating of gypsum; at this time I am unable to determine this with
certainty. The
Alaskan glendonites so far available to public scrutiny are found at the
northern extremity of the state, on Carter Creek about 3 miles above where
it meets Camden bay. As is typical they are found in a semi-hardened silt
formation, as concretions, on the banks of a small tributary where it meets
the creek.
"At
Manning Point and Barter Island, along the Beaufort Sea coast northeast
of Carter Creek, are two coastal localities with sediments that have been
referred to the Nuwok Member (Brouwers and Marincovich, 1988; Marincovich
et al., 1990). At the Manning Point locality, a coastal bluff of massive
mudstone crops out along the eastern length of the island. A distinctive
horizon containing concretions, concentrations of valves of the mollusk
Thyasira Alaskana, and large crystals of the mineral glendonite occurs in
the middle of the exposure. This horizon is identical to one found at the
type locality of the Nuwok Member, and the two horizons are inferred to
be coeval (Brouwers and Marincovich, '1988).
"The ubiquitous
presence of glendonite crystals has been used by field geologists to identify
the Nuwok Member. Rare glendonite crystals have been found in a few exposures
of the Gubik Formation (e.g., at Fish Creek; C. A. Repenning, pers. comm.
1989), but an abundance of glendonite is diagnostic only of the Nuwok Member
on the Alaskan North Slope. Microscopic glendonite crystals are found in
the mudstones stratigraphically above the distinctive horizon at Manning
Point as well as in mudstones on the north side of Barter Island, where
the concretion-mollusk horizon does not occur". [Late Pliocene Paleoecologic
Reconstructions Based on Ostracode Assemblages from the Sagavanirktok and
Gubik Formations, Alaskan North Slope -- Elisabeth M. Brouwers]
Nature's Jewels
Rock Shop & Lapidary, 5851 Arctic Boulevard #B, Anchorage AK 99518 --
907-349-7863
Joe and Bobbie Turnbow's Nature's Jewels is top-notch -- not only do they
have on hand an excellent selection of the rocks, minerals and gems of Alaska,
they also have a wide range of A-1 specimens from many other places worldwide.
Joe didn't have any glendonites in the shop when I was there in August of
2008, but he does now! Joe said in an email that he wasn't going to sell
any, so I will need to send him a nice batch of pseudos for his "unusual"
shelf. The
Central Texas Gem and Mineral Society had a
great article about Joe Turnbow in their January 2008 newsletter.
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