Emeralds are gem-quality specimens of the beryl mineral family with a rich, distinctly green color. They are found in igneous, metamorphic, and sedimentary rocks in a small number of locations worldwide. For over 5000 years, emeralds have been one of the most desirable and valuable colored gemstones.
For example, the Agway Elevator was built on a concrete mat 3 feet thick which in turn rests on a natural foundation of stiff clay. But whatever the foundation for the elevator was, be it wood pilings or concrete slabs, construction of the elevator itself could begin once the base was completed.
Shafts are vertical or inclined passages which connect the underground workings of the mine with the surface. The top of a shaft is called the collar. Shafts are primarily used for haulage and personnel access.A secondary shaft which has been driven down from within the mine is called a winze.A secondary shaft which has been driven upwards from within the mine is called a raise. Winzes and raises are mainly used as air shafts, ore chutes, manways or for exploratory purposes.ithin a drift, the roof is called the back and the side walls are called the rib. The floor may sometimes be referred to as the sill. Headframes are wood or steel structures constructed over a mine shaft or winze to support pulleys used with cables and hoists for haulage and access.