052120b

This rock has been through a lot. It began its existence in the Jurassic as a shifting sand shoal composed of tiny calcite spheres called ooids. The shoal was buried, and the ooids were cemented together with delicate crystals of calcium carbonate. The rock was now a limestone. Later, many of the ooids partially dissolved. Perhaps at about the same time, all of the limestone was turned to dolomite. The cement crystals became solid dolomite (solid bluish white curving areas in the picture), but the ooids still had a lot of holes in them (ovoid bluish or whitish areas). Also, some of the water-filled spaces among the original ooids had never been filled with cement (three dark blue areas with concave boundaries in the upper middle, middle, and lower middle of the picture). After a long time, thousands of feet of rock had buried the former shoal, and because it was so full of open spaces (dark blue) it was crushed.