Re: When a body is buried, how long before the skeleton turns to dust?

An unembalmed bodies buried six-feet deep in ordinary soil without a 
coffin takes ten to twelve years to decompose down to the skeleton.  It 
takes about 300 years for the bones to fully decompose under those 
circumstances.

Bodies left on the surface in temperate climates could decompose within 
four to six weeks.  The higher rate is due to the action of insects and 
animals eating away at the bodies.

Embalming slows down the decay of the body by a factor of two to ten, but 
it doesn't alter the rate of bone decay.

Check out the book "DEATH TO DUST" by Kenneth Iverson, published by Galen 
press.