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.
Not all gases are flammable. eg carbon dioxide, nitrogen or helium. Flammable gases are those which react easily with oxygen in the air to cause combustion... such as hydrogen, methane or propane etc. Even flammable liquids are flammable only because they give off a flammable gas at temperatures below. Gasoline evaporates at room temperature into a mixture of flammable gases which are far more flammable than the liquid itself.