Slime Crystals are one of many materials used to craft and maintain tools in Tinker's Construct. It is a non-metallic material that can be worked directly from the Part Builder. Using Slime Crystals to make tool parts gives tools the Slimy ability, giving it greatly increased durability And the ability to randomly spawn small blue slimes when fighting.
A Slime Crystal is made by smelting Slimy Mud in a Furnace. The resulting crystal will be either blue or green, depending on if the player used Gelatinous Slime or vanilla Slimeballs.
Slime Crystals can be used in the Part Builder, making any part from a pattern. Slimy tool parts have high durability, low reinforcement, high handle modifier, and good speed. However, this comes at the cost of not being able to mine higher-tier materials. However, because of blue slime's excellent handle modifier (Best for any non-metallic material, and the second best handle modifier overall, at par with Ardite and just below Manyullyn) it is commonly used for tool handles. Both blue and green slime tool parts can be found in village tinkerers.