[meteorite-list] Micromounts and weights - Standards Vary

From: Michael Gilmer <meteoritemike_at_meteoritecentral.com>
Date: Fri, 1 Jul 2011 17:41:32 -0400
Message-ID: <CAKBPJW89WdFyEEg=-6HDaN3bokTkUPoyM_96keS80mm=zMp7GQ_at_mail.gmail.com>

Hi Sergey and List,

I agree that it is difficult to measure very tiny 1mg specks. When
they are too small to handle, I just call them a "Bessey Speck" or
"tiny speck" and leave the weight unstated. A photo with items for
scale with show the buyer what to expect.

If static electricity can move the speck, then it is less than 1mg! ;)

Best regards,

MikeG

---------------------------------------------------------------------------------
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Best regards,
On 7/1/11, Sergey Vasiliev <vs.petrovich at gmail.com> wrote:
> Hi All,
>
> Actually I always thought that trying to measure something like 0.001g is
> very difficult.
> If you measuring such a small thing on the same kind of spring scale at the
> sea level and at 500m above the sea level, the scale will show you a
> different result.
> Simple example:
> http://www.edinformatics.com/math_science/mass_weight.htm
>
> Best,
> Sergey
>
>
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com]On Behalf Of Michael
> Blood
> Sent: Friday, July 01, 2011 11:03 PM
> To: Met. Mike Bandli; 'Michael Farmer'
> Cc: Meteorite List
> Subject: Re: [meteorite-list] Micromounts and weights - Standards Vary
>
>
> Mike,
> I checked this out and was confused. The first statement:
> " METTLER TOLEDO AT261 0.01mg Counting Scale in HardCase"
> Implies accuracy down to a tenth of one mg! That is .0001g
> HOWEVER, the first part of the description reads:
> Weighing Capacity:205g Repeatability:(0-50g)+/-0.015mg
> Linearity:(10g)+/-0.03mg Stabilization:(typical)8-12sec
> What the h*** does that mean? It sounds like a maximum
> Capacity of 205g, but "repeatability:(0-50g)+/- 0.015" seams
> Like it is saying it can be off by 15mg!
> THEN: "Linearity:(10)+/- 0.03mg Stabilization..." sounds
> Like they are saying it could be off by 30mg.
> How do others read this?
> Michael
>
> On 6/30/11 5:11 PM, "Met. Mike Bandli" <fuzzfoot at comcast.net> wrote:
>
>> Yes, and for those serious about weights, I would highly recommend a
>> refurbished Mettler unit similar to this one:
>>
>> http://tinyurl.com/3dz8udc
>>
>>
>> ----------------------------------------------
>> Mike Bandli
>> Historic Meteorites
>> www.HistoricMeteorites.com
>> and join us on Facebook:
>> www.facebook.com/Meteorites1
>> IMCA #5765
>> -----------------------------------------------
>>
>>
>> -----Original Message-----
>> From: Michael Farmer [mailto:mike at meteoriteguy.com]
>> Sent: Thursday, June 30, 2011 4:55 PM
>> To: Mike Bandli
>> Cc: Michael Gilmer; Meteorite List
>> Subject: Re: [meteorite-list] Micromounts and weights - Standards Vary
>>
>> I use a multi-thousand dollar scale, you are right about the cheap scales,
>> have bought several for the field, they are worthless.
>> Wanna sell the small stuff, make the investment to do it right.
>>
>> Michael Farmer
>>
>> Sent from my iPad
>>
>> On Jun 30, 2011, at 4:52 PM, "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
>>>
>>> --
>>>
>> --------------------------------------------------------------------------
> --
>>> -----
>>> Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
>>>
>>> Website - http://www.galactic-stone.com
>>> Facebook - http://tinyurl.com/42h79my
>>> News Feed - http://www.galactic-stone.com/rss/126516
>>> Twitter - http://twitter.com/galacticstone
>>> EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564
>>>
>> --------------------------------------------------------------------------
> --
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Received on Fri 01 Jul 2011 05:41:32 PM PDT