Values for Metals, Gemstones, and Other Materials (1965)
From GURPSworld Wiki
Prices are in US dollars.
Metals
Platinum, $100 oz.
Gold, $35 oz.
Silver, $1.30 oz.
Copper, $.35 lb.
Lead, $.15 lb,
Gemstones
The value of a gem is ($1 x C2+$4 x C) x V, where C is the weight of the gem in carats and V is the Value modifier for the gemstone. Value modifiers for specific gemstones are provided below.
Diamond, 40
Sapphire, 35
Emerald, 35
Garnet, 35
Cat’s Eye, 30