Many items in rend can be salvaged, which breaks them down into another set of items. Examples of items that can be salvaged include geodes (which are salvaged into appropriate types of crystals), wolf abdomens (which salvage in to various things a wolf might've eaten), and meat (which salvages into animal blood).
To salvage an item, use RMB on the item in your inventory, and then click salvage on the popup menu.