Blade Composition
The tip or blade of any muscle-powered melee or thrown weapon that inflicts cutting or impaling damage (excluding wooden stakes, and powered weapons such as chainsaws) is assumed to be stone at TL0, bronze at TL1, iron at TL2, and steel at TL3+. For instance, a knife would be stone at
TL0 but steel at TL3, while a greatsword would always be steel, as greatswords don’t exist before TL3. Blade composition modifies effective quality when parrying a very heavy weapon.
Weapons made from outdated materials are usually available at cheap-quality prices.
- Stone (TL0): A stone blade has an armor divisor of (0.5) on its cutting and impaling damage, and receives no damage bonus for being of fine or better quality. Regardless of actual quality, treat a stone blade as cheap for breakage purposes when parrying a swung weapon made of metal or other high-tech materials.
- Obsidian (TL1): A blade made of volcanic glass is very sharp, but easily broken or blunted. Treat as a good-quality stone blade, but with +1 to cutting and impaling damage (as if fine) and +2 to breakage (as if cheap). It loses its damage bonus if used to parry any weapon (but not an unarmed attack) or to strike DR 2+.
- Bronze (TL1): A bronze blade receives no damage bonus for being of fine or better quality. Regardless of actual quality, treat a bronze blade as cheap for breakage purposes when parrying a swung weapon made of superior materials (e.g., iron or steel).
- Iron (TL2): An iron blade receives no damage bonus for being of fine or better quality. Regardless of actual quality, treat an iron blade as cheap for breakage purposes when parrying a swung weapon made of superior materials (e.g., steel).
- Steel (TL3): Steel is the “default” material for blades. Use all rules as written.
- Plastic (TL7): “Plastic” includes carbon composites and other advanced, nonmetallic materials. Halve weight and double cost. Blades cannot exceed good quality (and are often cheap). Treat them as equivalent to steel for breakage – but their low weight means they’re more likely to encounter a heavier weapon. Weapons that do only crushing damage (clubs, batons, etc.) are also available, in the usual quality grades. The primary benefit of plastic weapons is that metal detectors cannot detect them!
Silver Weapons (TL1): Those who must combat demons, werewolves, etc. may desire silver weapons. Silver weapons typically require a special order from an artisan. Solid silver melee weapons or arrowheads cost 20 times list price, and break as if of cheap quality. Silver-coated and -edged weapons cost only three times list price, and use the breakage properties of the underlying material. Silver bullets (TL4+) must be solid, and cost 50 times list price!
Silver weapons only inflict extra damage on creatures with Vulnerability (p. 161) to silver. For a silver-coated or -edged weapon, reduce the wounding multiplier: ×2 becomes ×1.5, ×3 becomes ×2, and ×4 becomes ×3.
Source: GURPS 4th - Basic Set - Combined, page 275 (PDF page 277)