RARE IMPACTITE Glover Bluff Wisconsin USA 648-gr. (one-pound, 6.8-oz.) VERY Hard

Description

There is, quite understandably, a growing interest in large meteorites and asteroids. That such large objects have struck Earth in the past, and will continue to in future, is something scientists have only fully begun to appreciate since about 1980. At present, there are over 190 recognized impact structures, and, every year, one or two new ones are being confirmed. Perhaps one hundred potential sites awaiting study. Confirmation of new impact craters takes a lot of time because there are probably more workers at the average McDonald's Restaurant than geologists who study impact craters!
The impact creates a crater far larger than the size of the impacting body.
Small craters resemble simple bowls; larger
ones may contain a central uplift or peak and multiple rings.
Local or area rock and soil are vaporized. Fallback material
may fall into or around the fresh crater, or be bourne many km (miles) away. Melted
fragments may be tossed at high
speed becoming aerodynamically-sculpted as impact melt glass bombs. Or
soil and sand may quickly cool into impact
melt glass. LONG after erosion has erased signs of craters, such
impactites
may remain.
Offered here for your kind consideration is a very fine impactite, a rough broken chunk of VERY hard impact melt breccia from the
Glover Bluff, Wisconsin, USA impact crater, likely the least-studied crater on Earth.
The quarry was active for years, and I understand
it is now closed, so such specimens are rarely available. It is 11.5 x 8.5 x 6.0-cm (roughly 4 1/2 x 3 1/3 x 2 1/3-inches) and it weighs
648-grams
(one-pound, 6.8-oz.).
Note the one-cm (~3/8-inch) brass cube for scale is not included. I will include the roughly
roughly 5.0-cm (2-inch) wide descriptive label printed on cardstock
(as shown)
that
identifies the
specimen, the crater size and age,
and states this is
from the collection of Richard Dreiser
.
I believe this chunk may offer valuable insights if you cutting cut slices from it, or make thin slices.
The Glover Bluff meteorite crater is located about 6.4-km (4-miles) south of Coloma, Wisconsin in the midwestern United States,
close to 153-km (95 miles) from where I live. The crater is roughly 8-kilometers (5.0-miles) in diameter and the age is estimated
to be less than 500 million years (making it from the Cambrian or younger). The crater is exposed at the surface. So far as I know,
the Glover Bluff Quarry is now closed to collectors.The site is among the least studied in the world, in part because the uplifted
central area has for decades been actively quarried for dolomite beneath the moraine left by retreating glaciers. Ironically, the
very evidence supporting a meteoritic impact origin uncovered in the quarrying process was systematically destroying the crater.
Such evidence includes a central bulge, dipped strata, the presence of "shatter cones" (although likely these were no longer as
common as they may once have been), and, "impact breccia." There are red, yellow, and tan varieties, sometimes found in a quite
colorful apparently melted mixture.
The yellow is ancient sandstone. My general impression is that the red variety lies directly atop the ancient sandstone.
The layering show the astonishing effects of resurge sand sloshing back into the crater. At least that is my impression.
This sample may contain broken fragments (or shards) of quartzite and other rocks, including breccia-in-breccia. As I already
mentioned, it is VERY hard and I haven't the patience to cut it.
I would love to keep this specimen, however, after sixty years of collecting, I'm retired, and I must be getting rid of some of my most
cherished specimens. I can ship this via First Class Mail within the USA. I can also combine other winnings and ship in the same
carton to save you postage.
IMPACTITES may be mixtures of local shattered and melted local or area rock and dust deposited many kilometers or miles away.
These mixtures may harden into new rock types called impact breccia or fallback breccia. Monomict breccia has only one variety
of rock fragments while polymict breccia has two or more varieties of rock, sometimes with melted glass.
The pressure of impact from a comet or asteroid is far greater than the force of an earthquake, tsunami or super-volcano. It can
affect a number of local or area Earth rocks, sand and soil, sometimes profoundly so. Long after a meteorite impact crater has
disappeared from the landscape, buried or eroded away these, "impactites," may yet remain.The impact creates a crater far larger
than the size of the impacting body. Local and area rock and soil are vaporized. Small craters resemble simple bowls; larger ones
may contain a central uplift or peak and multiple rings. Melted fragments may be tossed at high speed becoming aerodynamically-
sculpted as impact melt glass bombs. Or the soil and sand may quickly cool into impact melt glass.