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.
The mine shaft is used to admission to an underground mining capability. Horizontal workings off the shaft are known as drifts, galleries or levels. These expand from the central shaft towards the ore body. The point of contact among these levels and the shaft itself is called the inset, shaft station or plat.nderground mining is selected when the rock or mineral is so far to reach using surface mining. Shaft mining is the kind of mine that you normally see in movies where the miner travels straight down into a profound, dark tunnel until he reaches the base.