as a pragmatic lapidary & designer i look for the least
complicated way to attain the results i need. for drilling pieces
of quartz, the next notch down from diamond on the mohs hardness
Huh? I normally let minor inaccuracies pass but this one has to be
pointed out. That “notch” leaves out a few rather important
minerals. Diamond is Mohs 10, and it’s not a proportional scale.
Diamond is many times harder (in some crystal directions!) than the
next-hardest mineral, corundum (sapphire and ruby) at 9. Then
there’s chrysoberyl (alexandrite, cat’s-eye and golden and green
chrysoberyl) at 8.5. YAG (a man-made “garnet”) is 8.25. Next in line
are spinel, topaz, taaffeite, rhodozite. phenakite and some natural
and synthetic beryls at 8. The 7.5 “notch” is occupied by some
beryls, and zircon, almandine garnet, hambergite, euclase, gahnospinel
and gahnite. Several members of the garnet group (rhodolite, pyrope,
spessartite) range between 7 and 7.5, as do tourmaline, andalusite,
iolite, and staurolite.
Now we’re down to quartz, which shares the 7 position with grossular
garnet, danburite, dumortierite and occasional chalcedonies,
peridots, jadeites, andradite garnets, axinite, and saussurite.
Some quartz minerals like chalcedony, agate and jasper can range from
6.5 to 7 and a little above.
I agree with your solution to the drilling problem, although if a lot
of drilling is required it would be better to contract the job out to
someone with modern sonic drilling equipment. Back when I started in
lapidary work (dinosaur coprolites were not yet fossilized!), we did a
very satisfactory job of drilling quartz using mild steel or brass
drill bits with loose silicon carbide grits for abrasives (all
underwater of course). Diamond bits, especially at current prices,
represent an order of magnitude technological advance and are a
bargain to boot.
I’ve seen beautiful examples of drilled quartzes accomplished by
pre-Columbian societies in South America. The work was probably done
with bow drills and alluvial garnet, beryl or corundum sands as
abrasives. Such skills have existed for millenia. The Romans traded
diamond-tipped drill bits over 2,000 years ago! The diamonds probably
came over the Silk Road from the fabled Golconda mines in India. The
ancients were very quick to observe the physical properties of various
minerals and how they could be turned to an advantage in commerce.
Sorry for the lecture.