Ivory and other things

There was a thread not long ago about how to tell ivory from bone or man-made substitutes, and the concensus seemed to be that it is difficult to find a foolproof criterion which will be both non-destructive and accurate in every case.

If you have the scales separate from all the metal parts, specific gravity is a useful indicator.

http://www.reade.com/Particle_Briefings/spec_gra2.html#I

They make ivory 1.84, but I have seen it quoted at 1.8. This website says "S.G. 1.7 - 2.0: 1.70 -1.85 (elephant and mammoth); 1.80 - 1.95 (hippopotamus); 1.9 -2.0 (narwhal, sperm whale, walrus and warthog), and claims that ivory fluoresces blue-white under ultraviolet light.

http://stoneplus.cst.cmich.edu/zoogems/ivory.html

The same website's section on bone gives its specific gravity as 2.30 - 2.57, but quotes another authority at 1.95 - 2.20. I googled various figures (You don't suppose I knew all this in advance, did you?), but all were heavier than ivory.

http://stoneplus.cst.cmich.edu/zoogems/

That is minus the hollows and porosity of most whole bones, but there aren't any in razor scales. It should be noticeably heavier than ivory, and most substitutes are considerably lighter. Bakelite should be about 1.25, and many other plastics will float in water, i.e. are under 1.00.

Specific gravity isn't a lot of use unless you can find out what it is. But anybody who does jewellery work or reloads firearm cartridges is likely to have a very accurate scale. Just suspend the object on a human hair (to avoid interfering with weight and volume), and weigh it first in air, and then suspended in water. The dry weight divided by the difference between the two weights is the specific gravity. Floating "ivory" is a dead giveaway, and I think that if you have another object of similar shape and size, you should be able to see a difference in the rate at which they sink to the bottom of a deep tank or swimming pool.

Incidentally I sometimes eat ostrich meat, which is sold quite cheaply in Saudi Arabia, and the ostrich betrays his avian ancestry by having extremely thin-walled tubular bones. It really does look very hard and dense indeed, as you would expect from the ostrich's need to run and kick. I've only ever seen short, sawn tubular pieces, but if you can find a piece long and flat enough, it might be the best bone of all for razor scales.