[meteorite-list] Micromounts and weights - Standards Vary

From: Michael Blood <mlblood_at_meteoritecentral.com>
Date: Fri, 01 Jul 2011 13:37:31 -0700
Message-ID: <CA337E1B.1B6FC%mlblood_at_cox.net>

Hi Mike and all,
        I absolutely agree. I used to use a $500 digital and now
Use a $135 digital and I consider them both about as accurate
As the other ~ deduct one decimal point for absolute accuracy.
(it is likely far closer than that, but one should not proclaim
a specific weight, IE .007g (7mg) unless one has a serious
balance beam in an air tight setup. A royal pain in the a**
And extremely costly.
        However, for the most part, I always sell micromounts - the
Ones less than 10mg, based on VISUAL COMPARISON. That is
What I look for for my own collection... If I want something that
Is so small, then the size is far more important to me than the mass.
        BTW, a micromount has traditionally been defined as any
Specimen that fits into an old style 1" X 1" square display box.
The new, vastly superior membrane boxes are considerably larger
And can hold a decent sized macromount equally well as a micromount.
        Best regards, Michael

On 6/30/11 4:52 PM, "Met. Mike Bandli" <fuzzfoot at comcast.net> wrote:

> A little perspective on milligrams:
>
> There are a lot of meteorite mg weights out there that not accurate. We can
> thank these new, cheap Chinese digital scales that promise accuracies of +/-
> 1mg or less, which are a complete joke. I bought one in Tucson to test it
> out against my high-end calibrated machine and it was off by about 10 mg on
> average for pieces 50 to 100 mg and 5 mg on average for pieces 10 to 50 mg.
> Anything fewer than 10 mg - forget about it. The calibration weights it came
> with were even more laughable...
>
> In reality, in order to be able to accurately measure mg, you need a machine
> that has been recently leveled and calibrated in-situ. I have a recently
> leveled/calibrated mechanical scale whose tare changes by the hour due to
> changes in the weather. It even picks up the subtle vibration of the
> dishwasher downstairs.
>
> Bottom line - a $100 mg scale isn't going to get you the accuracy needed to
> accurately measure true mg. Since most people can't afford the hundreds to
> thousands it costs for an accurate mg scale, I don't expect most mg weights
> advertised to be truly accurate. They're close...
>
> Just my 2 mg worth (+/- 1mg)...
>
> ----------------------------------------------
> Mike Bandli
> Historic Meteorites
> www.HistoricMeteorites.com
> and join us on Facebook:
> www.facebook.com/Meteorites1
> IMCA #5765
> -----------------------------------------------
>
>
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Michael
> Gilmer
> Sent: Thursday, June 30, 2011 4:17 PM
> To: Meteorite List
> Subject: [meteorite-list] Micromounts and weights - Standards Vary
>
> Hi Listees and Micronauts,
>
> There has been some discussion recently about people buying
> micromounts from a vendor on eBay and not getting the weights they
> were promised. I thought I would throw out some thoughts on micros,
> since those are my bread and butter.
>
> First, the definition of "micromount" is relative. There is no
> set-in-stone size bracket for what defines a micromount. It seems to
> me that the general consensus is that micromounts are in the 1g range
> for the more common types and sub-gram in weight for the rare types.
> Very rare falls or planetaries are commonly sold by the milligram.
> Rockhounds tend to equate meteorite micromounts with mineral
> thumbnails. But generally speaking, most micromounts on the market
> today are in the sub-gram (<1g) range.
>
> Ideally, a micromount should be visually appealing (such a well
> polished, thin part slice with good surface area to weight ratio) and
> big enough to identify the lithology of the type/fall, while at the
> same time being cheap enough to afford on a limited budget.
>
> The more preparation that goes into making a given micromount, the
> higher the price, generally speaking. At some point, it's not
> financially viable to put a lot of cutting and polishing work into
> piece of common find that is only worth a buck or two a gram.
> Smaller micros are difficult to work with during preparation, for
> obvious reasons, so many of the micromounts seen on the market are
> unpolished, rough, or broken.
>
> What motivates a person to collect micromounts varies from person to
> person, but the most commonly cited reason for buying micros is to
> temporarily fill a void in a type collection. It could be a
> petrologic type, a find from a given geographic area, a fall from a
> specific date, etc. Often a micromount is a temporary measure until a
> nicer specimen can be acquired, or until the needed finances to buy a
> larger piece can be saved up. For the very rare types and
> planetaries, a micromount might be the best hope for a collector on a
> restricted budget.
>
> There are a couple of schools of thought when it comes to dealing and
> selling micromounts - some dealers sell specimens by weight (by
> milligram, even for specks) or some dealers offer specimens by the
> piece (by eye/photo). For the most part, I am of the latter school
> that sells micros by the piece. That means I don't weigh each and
> every micromount, unless it is a very rare and valuable meteorite such
> as a planetary or historical fall. Each dealer has their own methods
> for handling micromounts and we those aren't really relevant to the
> discussion at hand.
>
> When weighing micromounts, one must use an accurate scale that is
> sensitive to 1 milligram - the good ones are used by diamond and gem
> dealers. There are many brands of these scales which range in quality
> and accuracy. When dealing with small specks that weigh a milligram
> or two, the readings can vary from unit to unit when weighing the same
> specimen. If a buyer pays for and is promised a micro that weighs
> 100mg, it better weigh 100mg and not 50mg or 80mg. Sometimes a buyer
> gets an added bonus because their personal scale is more accurate than
> the seller's scale and a promised 100mg micro might weigh 120mg or
> 150mg. If the seller is not sticking to a strict pricing scheme ($/g
> or $/mg), then ultimately what matters is if the buyer is happy with
> their micromount.
>
>> From a collector's standpoint, it pays to shop around for micromounts.
> Unless it's a very rare meteorite, it's easy to find several dealers
> offering similar-sized specimens for widely-varying prices. One must
> also pay close attention to the reputation of the seller and the
> provenance of rare specimens. Because micros tend to be small (some
> are downright tiny), it would be easy for an unscrupulous seller to
> misrepresent specimens as something more valuable than what they truly
> are. Chances are, if you are reading this mailing list, you are one
> of those people who can find a reputable source and who does their
> homework before sending payments across oceans on fiber-optic cables.
>
> My own personal meteorite collection (the pieces I keep in my cabinet
> and are not traded on my website) are mostly micromounts and I keep
> the majority of them stored in 1.25" gemjars with paper labels inside
> the bottom, under the foam. Some people prefer membrane boxes, small
> Riker boxes, or other storage and display methods, but that is the
> subject of an entire debate of it's own. The most commonly-seen
> container on the micromount market is the gemjar, and thus it is a
> general rule of thumb that if a specimen will fit into a gemjar, then
> that specimen could/should be called a "micromount".
>
> Best micro-regards,
>
> MikeG

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Received on Fri 01 Jul 2011 04:37:31 PM PDT