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November 16, 2011

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Interesting puzzle. I don't have any insight as to "exactly" what it might be, but interpreting the quotation gives me some room to speculate. Mildred calls it "coarse" grey sand. I don't suppose she's strictly following the Wentworth definition of "coarse", but one would think that all other factors being equal, coarseness alone would make it less likely to be blown about by the wind. "Coarse" sand isn't what I'd think of for a polishing compound: typically abrasive polishes have a very fine/powder consistency. Perhaps the jade carvers ground the "coarse" sand prior to use? Anyway, something that polishes jade (presumably nephrite) but doesn't scratch it would have to be equal in hardness or nearly so, but not much harder. Nephrite's Mohs hardness is 5.5-6 (Wikipedia). I'm thinking something like apatite (5) or titanite/sphene (5-5.5). Both are significantly heavier than quartz sand, and could conceivably form placer (or even aeolian?) concentrates. Barite/baryte comes to mind as a heavy mineral, but its hardness, 3-3.5, wouldn't be much good for polishing jade. Pure feldspar sand would probably be the right hardness, but its density is about the same as quartz sand. I hope you let us know if you find out!

Sources mention corundum, quartz, and garnet. Sources are often lead-authored by Margaret Sax at the BM: http://www.britishmuseum.org/the_museum/about_us/staff/conservation_and_science/margaret_sax.aspx

Thanks for the reminder of those extraordinary women. Have you encountered the novel of that name, by Sir Compton Mackenzie? A very different business.

Howard and Richard, many thanks - as always - for your ideas. The hardness (and density) criteria are important; I thought that I had come across something of interest when I saw reference to a titanite placer deposit in Mongolia - but a more direct source did not mention the mineral as one of the constituents. My current line of enquiry (after a garnetifeous detour) is following up on the suggestion of corundum and its habitat in China.- - the link to Margaret Sax is very interesting indeed.

Re Compton Mackenzie, I am well acquainted with "Whiskey Galore" but not "Extraordinary Women." But I came upon this description on the net: "Mostly unknown entertaining novel with many different types of aristocratic queer women vying for one another while vacationing in Italian villas." I'll give this some thought...

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