Crystal Shards are a placeable crafting material which may be naturally found in the Underground Hallow on Pearlstone or Pink Ice Blocks, requiring a Pickaxe or a Drill to harvest. They come in several different shapes and colors before they've been harvested. After being harvested, however, their inventory image is always that of a purple crystal. Placing Crystal Shards will result in randomly-colored versions, in a manner similar to the randomized graphics created when placing Books and Coral.
Crystal shards give off a very small amount of light and brightens occasionally, which makes them somewhat easier to find. The light it emits depends on the color of the crystal. Crystal shards also regenerate after a short period of time, hence one can easily make a farm with a long bridge of pearlstone blocks.
Crystal shards can spawn on halfblocks.
Crystal shards will, rarely, be dropped by demons in the underworld and always dropped by Arch Demons.