Spiderite is dropped by all Spiders, found mostly on the higher levels of the dungeon.
It is used to build the Itesmithy object, which is required for making all ITE armor and weapons. It is also used for crafting the Spiderbane Set, leather spiderite armor, spiderite swords and arachnid bows. Unlike most of the other ITE items, spiderite weapons and armor require iron rather than copper.
All Goblins drop Goblinite. These are found primarily at the upper levels of the dungeon.
It is used to craft the Horde Set, leather goblinite armor, boots of haste and goblinite spears. All goblinite items require copper.
The sneaky Snicker blades drop Snickerite.
It is used to craft the Stealthy Set, leather snickerite armor and snickerblade blades. The snickerite weapon is unique in that it is the only ITE item that requires both copper and iron to craft.
Any of the malicious Ogres can drop Ogreite. These are found only at the lowest levels of the dungeon.
It is used to craft the Beastly Set, leather ogreite armor and ogre smashers. These are the best ITE items currently available in the game, and are inferior only to silver, gold and special equipment.
Only The Burning Pet drops the rare Burnite.
It is not currently used for anything.