by Jim Tobin

 

Meteorites, Tons, Grams, Milligrams, How Much Do They Weigh?

In this world of digital everything one of the charming pieces of equipment that is quickly disappearing is the mechanical scale. Many collectors still have a triple beam scale of some kind for weighing heavier specimens but for the small ones it is all digital.

I have no digital scale, we use one at the business office, but I donít own one. However, mechanical scales are one of the things that fascinate me. I have quite a few. I have old and antique single beams and triple beams, but I use mainly two real beauties for actual weighing.

For most applications my 0-2kg Torbal will give accuracy to about one hundredth of a gram. It is like all balances only as accurate as the weights that are put in the pans. Fortunately I have options to ensure that the weights are accurate. You can use the balance itself to make weights of increasingly larger size. The scale has a sliding weight on a beam for 100 grams. So it is no trick to make a 100-gram weight that is perfect and then use it in the right pan to create a 200-gram weight and then place that in the pan with the first and make a 300-gram and so on till you reach the capacity of the machine. Of course you could do what I rarely do and that is just buy what you need, in this case a set of precision weights. What you will find in reality is that any set less than very high quality will have weights that are near but not at their stamped value. Even digital scales often come with a 50-gram or other size calibration weight these however are very accurate.

As I said though I have options to ensure the accuracy of the weights for the Torbal and that is my Mettler scale. It only has a 160-gram capacity but it is accurate to fractional milligrams. It is an engineering masterpiece. With internal precision ring weights and an amazing damped beam that uses lenses, mirrors, and prisms to project an image of a scale; it is my choice for any precise weighing. That is unless the object weighs less than a fraction of a gram. Then I bring out the rarely necessary Christian Becker scale. I have two of these and, I have offered one to Paul but he hesitates to take it. It reminds him of his days in quantitative analysis I think. It is easy to fall asleep using this one. He told me a story of a test for a class. He had to weigh a small piece of paper, and then reweigh the paper after touching it to determine the amount of skin oil absorbed. It is as I said rarely used for it requires a permanent vibration free station. Even the Torbal must be used with the specimens in reach for once it is leveled and zeroed shifting your weight will affect the readings if it is just used on a cabinet as I do. You think your floor is solid, its not. The same thing goes for the Mettler only more so. But zeroing it is far easier.

With the emergence of many rare and exotic types of meteorites the last few years, weight has become a concern. With Lunar, Martian and some others selling for thousands of dollars per gram, accuracy of weighing becomes a real issue. I have heard of dealers taking their fragments to precision scales for weighing. I wonder if digital scales will come along that will be up to the task and how much will they cost. Some of the digital carat scales are pretty good, and I saw a lot more of them in use this year at Tucson.

Just for fun I got out some of the smallest specimens in my collection and weighed them. I have some Wabar glass pearls I weighed one of those. And I thought it might be of interest to let you know how much the metallic spheres from Meteor Crater weigh. All 18 tiny metal spheres from Meteor Craterís soil that were in one tiny glass bottle weighed 0.0120 grams.  I sometimes check the scales by weighing individual flower seeds. On one occasion I was working with the Christian Becker scale and a small gnat was flying around inside the scale while the door was up. I joked to my Dad who was watching that if it landed I would weigh it.

The Wabar pearl, which is pictured here, weighed 0.06223 grams. 

 
 

Small Saratov chondrule weighs 0.0075 grams.
 

The large Saratov chondrule weighs a whopping 0.038 grams.

 
 

The single flower seed shown here weighed 0.0014 grams.

 

Big or small there will never be anything quite as fascinating as these pieces of other worlds for me.  Now let me see what can I weigh next? Maybe an ancient seed captured and held in that hank of woolly mammoth hair I have. Now where did I put that. Was is over here? No. Maybe in this drawer. Oh sorry, Bye till next month.