Block of the Week: Obsidian

Obsidian forms sharp edges because of its chemical structure. It’s incredibly hard, and unlike crystalline minerals, which tend to cleave along their structural lines, obsidian has no crystalline structure. When it’s struck, the shockwave freely radiates outwards from the point of contact, creating curved ripples across the new surface. The edge can be so fine that it rivals even diamond. At best, a razor blade’s edge is about 300 angstroms across (30 nanometers or 0.00003mm), while a good obsidian edge is about 30 angstroms.

This means even today obsidian remains a valuable cutting tool, excellent for very fine procedures such as eye surgery. Creating clean cuts without tearing, obsidian wounds heal quickly and with less scarring than with a steel scalpel. The only problem is that the blade is so brittle, easily shattering if hit from the side. That’s why it’s not used so much as much more expensive diamond blades.

In Minecraft you might build blast-resistant walls with redoubtable obsidian, but outside the game it’s a far more fragile substance. But it’s no less useful.