' ... a crude but effective volume test. One takes a wooden box and fills it with ore, weighs it, then pours water in to the brim and weighs it again. Then you have the SG of the ore. True, not false or assumed.'
How do you compute specific gravity from that? ... drain the water out, measure it, and thereby obtain the volume of ore? [which is the hard part, once rock is broken out, to get its exact volume] .... cannot wrap my brain around this ..
... no wait, maybe i got it .... when you fill the voids with water you're filling up what is Not Ore .... right, got it
Dirt really fluffs up when you break it out, fractured rock would do even more so i expect, being more angular .... i've dug a few ponds years ago with a front-end loader, generally if they're any size you're loading trucks and the trick is to get the trucks close enough for efficiency ..... when you compute the in situ yardage, you can figure on about one highway truck load per every six or seven yards in situ, and then you load twelve or more yards of broken-out material in each truck ..... it fluffs up just about double, this was largely in a clayey conglomerate sort of glacial till .... dump a load of it on the ground, measure the height, then come back in a few weeks and it's five eighths as high .... and that's without erosion, just the grains of it settling and filling the voids ... when you take on a contract based on in situ yardage, it's vital to know the amount it fluffs up ... if it doesn't fluff up it's blue clay, it won't come out of your bucket, it won't come out of the trucks, and you're better off elsewhere, period
Only really accurate way to measure specific gravity would be to cut out an undisturbed piece of known volume, and weigh it .... but the water trick sounds like it would work, if you shook the box and got all air bubbles out
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