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Re: On measuring volumes of small pieces


well, calvin's monograph is not inaccurate. it is not unusual when the
weights and/or dimensions of items sold at phillips are rounded
down...especially the weights and dimensions of the small, exotic, and
expensive items. (on average, the dimensions are rounded down more than the
weights.)  

as those of you who have looked at a phillips catalog or the on-line
listing are aware, measurements are provided in millimeters. finally, given
the irregular dimensions of most fractured specimens, we opted to adhere to
the typical parameters utilized in the sale or bartering of meteorites, and
decided to forego volumes...and the requisite calculus that would have been
required.

best-
darryl


At 11:50 AM 5/19/98 -0700, Calvin Shipbaugh wrote:
>I read a news report that gave the dimensions of the Governador
>Valaderes recently auctioned as being .08 inches by .08 inches by .16
>inches.  This is a volume of only around .0168 cubic centimeters (2.54
>cm = 1 inch), which gives a density of .28 g divided by .0168 cm or 16.7
>g/cc.  I believe the dimensions given are not accurate or not maximum
>dimensions and somewhat larger values should have been used. A modest
>increase, say .1 by .1 by .2 inches, is not quite enough since then the
>volume is only about twice as much as the previous estimate yet still
>gives a density exceeding 8 g/cc.  Stone meteorites are typically less
>than 3.5 g/cc.  While I don't know SNC density I am certain it is
>nowhere near 8 g/cc, and assume it is under 3.5 g/cc. 
>
>Mass is fairly easy to measure for anyone with a good scale, but volume
>is another matter.  I would guess that for micromounts measuring the
>volume of what may be an irregular shaped and small piece is simply not
>easy unless great care is taken.  My hypothesis in lieu of a description
>by someone who was present is that the reported set of dimensions may
>have been based on using a ruler or tape graduated by sixteenths of an
>inch. It could have been easy with a quick measure of a nonsymmetric
>shape to err by a linear factor approaching two in any dimension when
>using the smallest subticks on the measuring stick.  This would then
>give the correct neighborhood for the density, given the .28 g mass.
>
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