I haven't had my hands on a "Dura-flint" but the material description sounds like the Ceramic Sapphire lap I use for gem cutting. Sapphire is aluminum oxide and when completely pure is colorless; the gems are colored by impurities. When fine grained materials are sintered together, most look white when finished, like my gem polishing lap. For industrial grinding wheels, you all may have aluminum oxide wheels? Same thing in a coarse grade.
Sapphire has about the same hardness and toughness as tungsten carbide; just under diamond, relatively. Gem cutters use the "Moh" scale where diamond is 10, sapphire 9, steels depending on carbon content and tempering range from 5 to 6.5, copper maybe 3, flints (a fine grained quartz mineral) about 6 to 7-, and glass is around 6. Steel hard enough to mark glass is very brittle. Knives would be in the 5-5.5 range on this scale. Axes for toughness sake, in the 5- range.
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Whatever material is used for a flint, it won't throw good sparks if it's dull. After a few shots, only tough materials like flint will still be sharp. A superhard material like ceramic sapphire can only be sharpened by diamond files, and careful knapping of the sort used in arrowhead making. The success/failure descriptions given above sound right for folks trying to use methods they're used to on a new material that has it's own specific needs.
I get a magnificent optically flat surface on the gems I polish with ceramic sapphire, but in my re-enacting persona, I use flint. It worked fine then, and just as well now. If I wanted a super flint, I'd just get an inline :youcrazy:
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Accuracy with flinters depends first on "follow through" where you hold through the delay time of ignition. The delay is in the pan, not the sparks made by the flint :shake:
My good rifle is second hand, purchased after I watched clover leafs made by the former owner. Offhand, I might add. It ain't the flint, it's the shooter. :thumbsup:
Jeff Smith