Low-priced stock that sells at less than $1.00 per share. Often highly-speculative and volatile, such as start-up mining companies. While, in general, penny stock are considered high-risk securities, some penny stock mature into less-speculative investments. All penny stock are traded over-the-counter.
In its natural form, cork is also a very good fire retardant, although cork dust is actually extremely flammable (because here the cell structure has been broken down). Impermeable: Cork has a magic chemical in its cell membrane that makes it completely impermeable to liquids and gases.
1 Cork floors are affected by direct sunlight and are prone to color fading. Keep blinds closed and direct sunlight off the cork floor on sunny days when possible or install UV protection on your windows.  Keep large animals with long nails off the floor as they can scratch and damage the cork.