Obsidian blades are still being used, relatively, regularly to this day.
Obsidian is a naturally occurring type of volcanic glass, that is extremely hard and brittle. It therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, it has even been used experimentally as surgical scalpel blades.
These blades are spectacularly sharp and smooth, being so sharp they are capable of cutting through individual cells. In comparison to steel scalpels which under a high power microscope appear more like saws than scalpels.
The obsidian edge when, cut correctly, is so sharp that it’s edge is 30 angstroms in width, a unit of measurement equal to one hundred millionth of a centimetre, that’s over 16.6 thousand times thinner than a human hair.
Their use however is limited due to their fragility, the blades are so thin that one miniscule move from side to side can shatter it, a problem steel scalpels do not have, needless to say a shard of volcanic glass being stuck in the patient is not a good thing.
Thus it takes a great deal of practice to be able to use these blades effectively with minimum risk, though this practice can pay off as it has been found that obsidian scalpels may reduce inflammation, healing time and scarring in the patient due to the lessened irritation caused by the blade.
Ultimately however the blades cannot be justified for use outside of very fine surgery, due to their higher cost from being hand made, their greater fragility and their little forgiveness for wayward movements.
So much so that the FDA has not approved them for use, despite the benefits they can bring, thanks to the higher tolerance they must be held in and their extreme fragility.
I wonder if trepanning will make a comeback in western medicine as well?
Further Info: http://edition.cnn.com/2015/04/02/health/surgery-scalpels-obsidian/index.html