Gemstone Block

Gemstone blocks can be crafted at a Heavy Work Bench in the Graveyard Mini-Biome. They require one gem and one stone block to craft, and when mined, drop only the gem. Every Gemstone block sells for 66 copper coins.

Trivia
Before 1.4.0.1, these blocks were unobtainable in-game, although a player could use external tools such as T-Edit to create them in a specified area.