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.
Quartz Crystals only emits enough light to brighten up a small area, so they are not effective for preventing spawns. However, they will not melt ice or snow like normal torches.
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: