[meteorite-list] Cold hunting

From: Tom aka James Knudson <knudson911_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:53 2004
Message-ID: <00c701c37819$1e94f560$3cc643d8_at_malcolm>

You could always burn the forest down and wait for the rain to wash the
black soot off the rocks to make the black crusted meteorites stand out
better. : )

PS. I am just kidding, please don't send any nasty replies.

Thanks, Tom
Peregrineflier <><
The proudest member of the IMCA 6168
----- Original Message -----
From: <joseph_town_at_att.net>
To: David Freeman <dfreeman_at_fascination.com>
Cc: <meteorite-list_at_meteoritecentral.com>
Sent: Wednesday, September 10, 2003 8:42 PM
Subject: Re: [meteorite-list] Cold hunting


> When I'm out, especially in wooded areas where enough light is penetrating
> the canopy, I'm pretty much encouraged by the fact that I can see seeds in
> droppings and debris that have been around for a long time, years. An old
> soda bottle covered with moss still in situ on the forest floor indicates
to
> me that a 5 month old rock should be visible as well. Some forest floors
are
> hard as asphalt. Other areas are as soft as sponge due to moss coverage
and
> rebound pretty heavy projectile intrusion. I'm trying to develop a
strategy.
> Does anyone have any suggestions. The first leaves of fall will obscure
the
> floor soon.
>
> Bill
> > Dear List;
> > One more point, I recognized my 53.7 gram meteorite at about 40 feet
> > away, and could confirm it to be meteoritic at about 30 feet by the
> > excellent crust. I would have not seen it at all probably if I were in
> > a vehicle, or riding a four wheeler.
> > My method is walk ten steps, scan left to the comfortable sight range to
> > see a golf ball sized black item (about 100 feet in good light and clear
> > skies), look across in front of me in a long sweep of the eyes, and off
> > to the right the same distance. Ten more steps (about 30 feet for long
> > legged me) and do it again. Keep in mind, no rocks in my playa lake bed
> > but I am sorting through antelope droppings, sheep droppings, and horse
> > piles. The main plan is to discern the meteorites from the animal
> > droppings. Riding a four wheeler, or bicycle wouldn't work, as there had
> > been previous 4 wheeler tracks in a methodic pattern running back and
> > forth across the playa and about 100 foot swaths and they failed to find
> > the one, and I am pretty sure it was one of my student meteorite hunters
> > that missed the golden opportunity by traveling too fast. Attention to
> > detail was what helped me locate that fusion crust, and handling and
> > looking at maybe a hundred pounds of individual NWA's really imprinted
> > that fusion crust in my mind. That was important to me...that and
> > putting down that remote control, the mouse, and getting out to where
> > the meteorites should be found.Time spent in the field where the
> > meteorites live is the most important factor for my find. They don't
> > usually come through the roof.
> > Best,
> > DAve F.
> >
> > Matson, Robert wrote:
> >
> > >Hi Norm and List,
> > >
> > >>As an exploration geologist, I spend at least 15-20 long days every
> > >>month wandering the alluvial fans and dry lakes of Nevada searching
> > >>for mineralized float (and, unofficially, meteorites!). Some of
> > >>the remote dry lakes are almost certainly unsearched, and can cover
> > >>many square miles.
> > >>
> > >
> > >You might be surprised. Aside from playas on military installations
(which
> > >in Nevada is a pretty big fraction!) I'm fairly confident that most
> > >of the major dry lakes in Nevada (and California) have been searched at
> > >least once by one or more competent meteorite hunters. Of course, they
> > >haven't been searched "completely"; indeed, no location can ever be
> > >completely searched due to the dynamic nature of playas.
> > >
> > >>Putting along on my ATV, I can give a reasonably large area a pretty
> > >>decent search. After several years of this, still NO cold finds.
> > >>
> > >
> > >This is actually a bit surprising, though I can think of a couple
> > >factors which could bring it about:
> > >
> > >1. your size threshold (how small a stone you will stop for)
> > >2. too broad a search image
> > >
> > >By broad search image I mean that your primary target (mineralized
> > >float) is so dissimilar to your secondary target (meteorites) that
> > >the subconscious pattern-matching that your brain is trying to
> > >accomplish will suffer. (It's hard enough picking out meteorites
> > >among terrestrial brown and black rocks).
> > >
> > >>I think the point may be that there's a pretty good chance that
> > >>stones have at some point fallen on most any square mile of earth's
> > >>surface.
> > >>
> > >
> > >Absolutely. Even if each fall produced only a single meteorite, in
> > >any square mile you could expect a fall about once every 5000
> > >years. However, the average number of meteorites per fall is
> > >certainly more than one (perhaps in the neighborhood of a half
> > >dozen?), so this improves things. Maybe a meteorite every 2500
> > >years per square mile (a complex problem that requires some
> > >Monte Carlo modeling to come up with a good figure). This leads
> > >to Norm's next point:
> > >
> > >>However, in most areas, survival times are short. In many areas,
> > >>erosion has erased the record. In other areas, deposition has
> > >>buried every trace.
> > >>
> > >
> > >Exactly. I liked this wording:
> > >
> > >>From the cosmic perspective, every square mile is created equal, but
> > >>for us grunts on the ground, that's far from the case. Some square
> > >>miles are just right. Most are not.
> > >>
> > >
> > >If you want to reduce search time per (cold) meteorite find (i.e.
> > >non-strewnfield), the #1 factor is "survival time" -- you must
> > >maximize it any way you can:
> > >
> > >1. Low deposition rate -- ideally a ~negative~ deposition rate: you'd
> > >prefer a surface that is "deflating"
> > >
> > >2. Low annual precipitation
> > >
> > >3. Minimal human presence
> > >
> > >Fortunately point #3 tends to go naturally with #2. It's only in the
> > >modern era of weekend warriors (and meteorite hunters!) that #3 has
> > >become an issue. Still, the historical importance of point #3 can
> > >not be ignored for iron meteorites. Chondrites wouldn't have been
> > >particularly useful to native Americans 500 years ago; irons certainly
> > >were.
> > >
> > >But detection isn't just about "signal" (signal in this case being
> > >the presence of meteorites); it's about signal-to-noise ratio (SNR)
> > >and scan rate. What else is sharing space with your meteorites,
> > >and how does this impact the rate you can search an area? It's
> > >not much fun looking for meteorites in a sea of basalt.
> > >
> > >Scan rate, incidentally, is the reason one should never hunt cold for
> > >meteorites with a metal detector. It is more than 50 times less
> > >efficient that visual searching. But you also don't want your scan
> > >rate to be too high or you'll miss the small stuff. Remember that
> > >there are far greater numbers of small meteorites than large ones.
> > >Searching in a car or truck is fine for finding the big ones, but
> > >most places that ~can~ be searched by car/truck in Nevada and
> > >California already have been. You'll have better luck looking for
> > >small meteorites, and this means getting out of your car and its
> > >limited viewing angles. Most of my searching is done on foot.
> > >
> > >An ATV is even better than walking: you're still close to the ground
> > >with an unobstructed view, but you have the comfort and convenience
> > >of motorized transport. ATVs can also get into distant areas that
> > >cars can't (and by extension, walking searchers).
> > >
> > >So to summarize: search old, simple surfaces on foot or by ATV,
> > >and you will eventually find meteorites.
> > >
> > >Cheers,
> > >Rob
> > >
> > >
> > >______________________________________________
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> > >
> > >
> >
> >
> >
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Received on Wed 10 Sep 2003 11:59:35 PM PDT