BY STEVE VOYNICK

Limestone is a great fossil medium; this fossil slab shows many forms of Devonian Period marine life.

In the world of sedimentary rocks that includes sandstone, siltstone, mudstone, shale and all intermediate grades, limestone is the star of the show. Although this fine-grained, often non-descript, grayish rock makes up only 10 percent of all sedimentary rock, it serves as an architectural stone and a vital material for the production of steel, chemicals, and cement. It is also an abundant source of fossils, the geological precursor of marble, and the host rock for the world’s great caves.

As the most widely mined mineral commodity, limestone hugely impact the global economy. Some 10 billion tons of limestone worth $90 billion are quarried each year, an amount roughly equal to 2 tons for every person on Earth.