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.
I have seen one answer saying secondary beams support main beams. Apologies, but this is totally incorrect. Main Beams ... as the name suggests are the main framing beams which play a role in overall stability of the structure frame. Stabillity is the foremost requirement for any structure. Once your frames are stable. Secondary beams are place on main beams to support other items like grating or chequered plate.