Gems

Gems are valuable crafting materials found underground. There are currently 7 gem types. Gems can also be placed on any side of a block after being mined. They are found in any underground layer, except for The Underworld.

With the exception of Amber (which requires an Extractinator), gems are found in the following forms;
 * Embedded within Stone Blocks.
 * In placed form on blocks underground, including sometimes in Underground Cabins, or rarely in the Dungeon.
 * As gem stashes, which are breakable background objects (similar to Coin Stashes), each resembling a rock with gems protruding.

Gems can also be found in higher concentrations in rare gemstone caves, which can contain multiple gem types lining and embedded within their Stone Blocks.

On the, mining gems also has a chance of yielding a Broken Heart during Valentine's Day.

Types
In descending order of rarity and value (rarest at the top):

Gemstone cave


A gemstone cave is a rare, irregularly shaped room often found in the cavern layer. It contains a high concentration of placed gems on multiple stone surfaces, as well as a few gems embedded in stone. Most gemstone caves contain one or two types of gemstone, but can rarely contain three or more types. The type of gem found in such caves is easily identifiable by the Gem Wall the cave utilizes, but this wall cannot be collected to obtain any items.

Trivia

 * Amber is the only gem that cannot be used to color the phaseblade, likely because of amber's nature in-game.
 * The stats of the staffs made from gems are directly related to the value of the gemstone being implemented, with the diamond staff having a higher damage than the amethyst staff.
 * Amber is an exception, being weaker than ruby staves.
 * In real life, some gemstones and minerals have been used as a dye, with azurite and cinnabar being especially the case. This could be interpreted as the colored robes found in the crafting menu.