You may be looking for Quartz Crystal (Applied Energistics)

Quartz Crystals are a naturally spawning gem added by XyCraft. It is a teal-colored crystal that can be mined without a tool. They are very common, and can be found at most, if not all levels. There are several stages of growth the crystal can exhibit, shown by the addition of more crystals to the cluster. Quartz crystals will naturally grow in size over time. Upon mining, the player receives at least one quartz crystal, more depending on the size of the deposit. These crystals can then be placed and will grow like normal. Quartz deposits will glow, giving off 8 blocks of light.

UsageEdit

As Quartz Crystals only emit enough light to brighten up a small area, they are ineffective for preventing spawns. However, they will not melt ice or snow like normal torches, which can be good or bad, depending on the situation.

Quartz Crystals also do minor damage to players touching them. This can be used for defense in a manner similar to cacti. In addition to this the crystals also destroy items when they are thrown on them.

Quartz Crystals are now used to craft XyCraft Liquid Detector blocks.

Quartz Crystals are a nearly pure source of Potentia and Crystallum aspects for use in Thaumcraft.

This video (Skip to 4:45) shows how to fix the Quartz Crystal stacking bug:

v · d · e XyCraft  Ores and Blocks  Xychorium •  Xychoridite •  Xychorium Block •  Xychoridite Brick •  Xychoridite Plate •  Xychoridite Platform •  Xychoridite Shield •  Xychorium Structure •  Aluminum •  Aluminum Ore •  Aluminum Block •  Quartz Crystal •  Sulfur  Grown  Corn Kernel •  Corn •  Popcorn •  Cob O'Corn •  Henequen Seeds •  Henequen Leaf •  Twine  Other  Sulfur Goo •  Sulfur Torch •  Aluminum Torch •  Aluminum Can •  Liquid Dyes