The Encyclopedia of Founding

Twelve hundred entries from the golden age of cast metal — how bells are founded, why brass is not bronze, what a cupola melts and a core withstands — by Simpson Bolland, the trade's great teacher.

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Hardness of Minerals

The hardness of minerals, beginning with the hardest, is as follows: Diamond 1, corundum 2, sapphire 3, topaz 4, quartz 5, feldspar 6, scapolite 7, apatite 8, fluor-spar 9, calcareous spar 10, gypsum 11, talc 12. See PRECIOUS STONES.

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