[meteorite-list] RE: Moqui Marbles
From: Matt Morgan <mmorgan_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:34 2004
I've collected Mogui Marbles myself in Utah a few years back. Your
explanantion of them as concretions is the one that I've always heard, and
never had reason to doubt it. As far as an impact explanation goes, I am
highly suspect. I did have a thin section made of a couple of them at the
time. No evidence of impact was found, and I would have found it if the
silica or any mineral for that matter appeared to have been "molten". I
could see that one would think this since the grains are coated, usually by
calcite which acts as the bonding agent. Occasionally, at the center of a
concretion, there may be a small piece of organic detritus. This was the
substrate that the other grains adhered to. Anyway, the area didn't look
like an impact site, nor was there any evidence in the marbles themself.
Thanks for bringing this up!
Mile High Meteorites
P.O. Box 151293
Lakewood, CO 80215 USA
From: Robert Verish [mailto:bolidechaser_at_yahoo.com]
Sent: Wednesday, February 28, 2001 8:07 PM
Subject: Moqui Marbles
Last weekend I had a display case at the San Fernando
Gem Fair in which I would show a meteorite, and then
right beside it, a look-a-like meteor-wrong. One of
these meteor-wrongs that I had displayed was a "Moqui
Marble", which I had labeled as a "limonite/hematite
concretion in sandstone". My explanation for how
these stones were formed started a lively debate among
the rockhounds in attendance at the show.
What I would like to ask you is what do you know about
the origins of these remarkably similar-shaped stones?
I know Dave Freeman has a comment or two that he
could make about these stones, but since you have been
doing impact-related field work close to this area, I
thought I would give you first crack at this topic.
It just so happens that one of our own brethren
[geologist] has muddied the waters, regarding the
origins of these stones. ("My sediments exactly."
said another geologist friend of mine.;-)
Here is what he had to say regarding these stones, at
"This material was formed in an impact site 12 miles
east of Escalante UT in an area known as 'Big Spencer
Flat'. The 'marbles' are composed of millions of
molten spheres condensing on sand grains that bumped
into and joined with other grains to form small
spheres that joined with others to become even larger,
with the hematite/silica coating always moving to the
outside, but leaving a thin coat on most sand grains
"Some larger spheres cooled below the melting point
during this process, so all steps of it can be seen.
Some 'marbles' landed in sand, others in limestone,
some have joined in almost every way imaginable. Most
of the crater has eroded away, but the remnants of
dikes created in the impact are still visible.
"The principle collecting area is in the new Escalante
Monument, but material was deposited on top of eroded
Navajo Sandstone as far as Lake Powell. I have yet to
determine if reports from Scofield Reservoir could be
the same formation, or a different impact. I am sure
the same process has produced 'Indian Paint Pots' in
sandstones from many time frames all around the world,
and are much like 'tektites.'"
The above quote is from Dave Cosby, a geologist who
has been doing some research on the Utah area where
Moqui Marbles are found. Dave believes that the
uniformly shaped stones were the result of a meteorite
impact in that area.
While we're on this subject, here is a "heads-up" for
the members of our eBay "Wrong Squad" - at these URLs:
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Received on Thu 01 Mar 2001 09:32:18 AM PST