Green Gem

"It's green and gemmy."

- Wilson The Green Gem can be used to craft the Construction Amulet, which raises Sanity as well as halves the resource cost of crafting items, and the Deconstruction Staff, which can be used to destroy structures/items and receive all of the resources used in their construction (barring gems).

Gathering
Green Gems are obtained by mining Ancient Statues, mining Broken Bits and Pieces of Stone, destroying Broken Clockworks, breaking certain Relics, opening Ornate Chests, and hammering Ancient Pseudoscience Stations.

Reign of Giants icon.pngReign of Giants
In the Reign of Giants DLC there is an alternative method of getting Green Gems, by destroying Tumbleweed.