Here are some gems I have drawn and coloured! Most of these were done following tutorials, which you can go to by clicking on each gem :D

Emerald Faceted Gem

Opal

Spectrolite

Triangular Opal

Rainforest Gem

Blue Gem

Black Onyx, Moonstone, Turquoise, Emerald Envy, Unakite

Abalone

Multicoloured Gem

Tree Pendant

White Mountain Variscite

Lace Agate

Purple Gem

Sea Sediment Jasper

Gold veined gemstone

Faceted Diamond, Turquoise, Mermaid Gem

Black Pearl, Turquoise, Opal

Pink Pearl