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Rock Crystal

ModAstral Sorcery

The Rock Crystal is an item added by Astral Sorcery. It is used to craft Crystal tools and collect Liquid Starlight in Lightwells. It can be acquired by mining Rock Crystal Ore. Each Crystal has three stats: Size, Purity, and Cutting.[1]

Rock Crystals can be turned into Celestial Crystal Clusters by throwing them into Liquid Starlight with Stardust. Doing so effectively randomizes the Celestial Crystal's stats.


Size can be increased by leaving the Crystal in Liquid Starlight, and decreased by grinding on a Grindstone. Reducing a Crystal's size to 0 destroys it. Attempting to increase the size beyond the maximum has a 1/6 chance of splitting it into two crystals with random Size and Cutting, one with the same purity, and the other with 0-9% additional purity.

The effect of size depends on what the crystal is used for:


Purity can only be increased by splitting maximum-size crystals in Liquid Starlight. Purity provides a transmission efficiency multiplier to things that focus or redirect starlight; the multiplier is the square root of the purity (so 25% purity provides a 50% multiplier). The higher the purity, the lower amount of size that will be consumed out of a Rock Crystal or Crystal Tool when grinding them.


Cutting can be increased by grinding a Crystal on a Grindstone, which also reduces its size. Cutting affects the effectiveness of Crystal Tools and the collection rate of Collector Crystals.

Astral Tome entry

Rock Crystal Ore: In the deepest reaches of the world, the intense heat and pressure form incredibly rare and fragile crystals. These crystals each have their own unique properties, and they seem to take in starlight with unusual ease. Due to the fragility of rock crystals mechanical hands are not careful enough when handling these ores.
Astral Tome