Just how sharp is obsidian? Extremely damn frikkin' sharp! I often regale students about the first time I knapped stone myself, a sad, sordid story that ends with a fountain of blood gushing from the tip of my index finger (not that I would ever exaggerate for dramatic effect or anything). Well, that bloody geyser was unleashed by a flake of coarse flint - and obsidian is much, much sharper than that. When I've given knapping demos using obsidian and inadvertently nicked myself with little obsidian flakes, they're so sharp that I usually didn't notice I was bleeding until I smeared blood all over myself - this made knapping look pretty bad-ass to at least one group of sixth graders I once gave a demo to.
But don't take my word for it! Lithic specialists often refer to the story of Don Crabtree (one of the people directly responsible for the rebirth of knapping in the 60's and 70's) insisting that he be operated on by surgeons using scalpels tipped with obsidian blades he had expressly knapped for the purpose. Buck (1982) reports some observations on this episode, as well as on experiments comparing the obsidian to steel scalpel blades, concluding that, at 30 angstrom (i.e., 3 nanometers; that's three billionth of a meter) obsidian is much sharper than even the sharpest steel blade, the cuts it produces heal just as well if not better than those made with a steel surgical blade, and contrary to some concerns, it doesn't chip or leave residues when employed to operate on soft tissue. Specifically, he observes that
In most fields of surgery, of course, a modicum
of sharpness suffices, and one feels comfortable
with the convenience of the modem disposable
steel blade. However, in many specialized areas,
scalpel blades and razor blades leave much to be
desired. Examples that come to mind are the
debridement of nerve ends for repair, microvascular
surgery, fine plastic work on thin skin (blepharoplasty,
for example) and ophthalmologic surgery.
Though one with faith in modem technology
cannot imagine that instruments equal to these
various tasks cannot be produced today, the fact
remains that no honed metal edge has matched
that of the glass blade to date. (Buck 1982: 269)
Since the results of that brief experimental study were published almost thirty years ago, however, there hasn't been much of a push for obsidian tipped surgical instruments. My guess as to why this might be the case, beyond inertia in surgical equipment trends, is that some of the practical aspects of making obsidian blades might have been underestimated by Buck, especially those concerning standardization in shape and thickness, along with the properties of various grades of obsidian.
Edit (03/03/2001, 10:45AM): Hey! This post was included in this week's ResearchBlogging 'Editor's Selection' for the social sciences! Sweet!
Buck BA (1982). Ancient technology in contemporary surgery. The Western journal of medicine, 136 (3), 265-9 PMID: 7046256