Rock Crystal Ore is a block added by Astral Sorcery. It is found at extremely low altitudes, typically in a y-coordinate range of 1 to 6. At night-time holding the Resonating Wand in either hand will cause the ore block to emit white particles upwards that are visible from the surface. Rock Crystal Ore can only be mined by a player, with diamond pickaxe at least, standing within 10 blocks of it, anything else (like a quarry) and the ore will drop nothing. Drop quantity is affected by the Fortune enchantment.
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.