Enchantment Glow disappears when walking into dark light levels

Holding an enchanted item (Sword, Pickaxe, etc) and walking into a low light level area (such as a dark cave) will cause the enchantment glow to slowly fade before becoming nearly impossible to see. Placing a torch or anything that causes a higher light level will cause the enchantment glow to be visible again, fading as you walk away from the light source.