Depletion time describes the length of time it takes to use up 50% of a mineral

I believe the answer is 80% of a mineral reserve. hope this helps!

Boy this is one of my strong points!
The president wanting to try to bring coal back even though the industry it self has already been gone for a long time. The environment suffered through these times due to the amounts of Air,and land pollution. The toxins and chemicals released when coal would burn would released huge amounts of Carbon Dioxide (CO2). The larger amounts of coal being released the more our atmosphere suffers!