Crystal Shard

Crystal Shards are a Hardmode crafting material found in the Underground Hallow, where they grow on Pearlstone Blocks, even when submerged in Water or Lava. Crystal Shards are randomly colored either pink or blue when grown or placed. They respawn randomly on Pearlstone blocks, similar to Mushrooms, making farming possible. Crystal Shards are most easily harvested using a Hammer, but can also be freed by mining the blocks surrounding them. They are easy to spot, as they are visible even in complete darkness due to a glow not unlike that of Demonite Ore.

In addition to being a common crafting material, Crystal Shards are also placeable; though they are not luminous enough to be of much use as a light source, they can be used to mark locations or paths so as to be seen in darkness, or as decoration. Although new Crystal Shards will only spawn on Pearlstone blocks, once harvested they can be placed on any block type.

Unlike most other resources that grow/respawn, Crystal Shards can grow in any direction (i.e. on ceilings and walls). They are quite common and sell for good money, and are used in the crafting of several useful items (in particular, Crystal Bullets and the Greater Healing Potion).

Crystal Shard farms can be created by placing Pearlstone blocks in the Cavern Layer to create an artificial Underground Hallow. The area should be properly "insulated" using open areas, Clay Blocks, or Wood, three blocks wide, to prevent spreading of the Hallow.