Straight from the old TSR Conan RPG from 1985, here are gem prices, which should make every GM's treasure-adjudicating job easier.
JEWEL TABLE
Cost/Jewel
5 cp Agate
1 sp Garnet
1 sp Mother-of-Pearl
2 sp Quartz
3 sp Amber
4 sp Chalcedony
5 sp Coral
5 sp Jet
7 sp Lapis Lazuli
7 sp Malachite
8 sp Onyx
1 gl Turquoise
2 gl Aquamarine
10 gl Pearl
15 gl Opal
30 gl Sapphire
30 gl Topaz
50 gl Amethyst
75 gl Jade
100 gl Ruby
200 gl Emerald
300 gl Diamond
cp = copper pieces; 10 coppers = 1 sp
sp = silver pieces; 10 silvers = 1 gl
gl = golden lunas; each luna is worth 10 sp
Note: The values of different gems and precious
stones may vary depending on the side of the stone,
the quality of the cut, and the clarity of the stone.
JEWEL TABLE
Cost/Jewel
5 cp Agate
1 sp Garnet
1 sp Mother-of-Pearl
2 sp Quartz
3 sp Amber
4 sp Chalcedony
5 sp Coral
5 sp Jet
7 sp Lapis Lazuli
7 sp Malachite
8 sp Onyx
1 gl Turquoise
2 gl Aquamarine
10 gl Pearl
15 gl Opal
30 gl Sapphire
30 gl Topaz
50 gl Amethyst
75 gl Jade
100 gl Ruby
200 gl Emerald
300 gl Diamond
cp = copper pieces; 10 coppers = 1 sp
sp = silver pieces; 10 silvers = 1 gl
gl = golden lunas; each luna is worth 10 sp
Note: The values of different gems and precious
stones may vary depending on the side of the stone,
the quality of the cut, and the clarity of the stone.