John D. Bloch
Consultant, Adjunct Faculty
Earth & Planetary Sciences Department
University of New Mexico
Albuquerque, New Mexico

Education: Ph D., University of Calgary, 1989; MA - Washington University in St. Louis, 1985; BA - New York University, 1972

Areas of Expertise:

"My research interests include the geochemistry and mineralogy of clastic sedimentary rocks and the origin and composition of sediments (petrology). Fine-grained clastic rocks (mudstones and shales) make up the majority of sedimentary rocks on the Earth and are the source for oil and gas on many continents. These rocks are composed of very small particles; the finest sand, silt and clay. The clay-sized particles are so small that they cannot be seen even with the most powerful light microscopes. To observe them, clay scientists use an electron microscope. Therefore, studying these rocks is challenging work.

"Shales and mudstones are also aquitards; that is, fluids cannot flow through them easily, so they control the flow of water, oil and gas in the subsurface. This is very important for the exploration and production of oil and gas and in understanding our supply of fresh water that comes from underground.

"Clay minerals are also important industrial materials that are utilized in everything from building roads and environmentally safe garbage dumps to making paper, medicine and cosmetics. They are used to clean up oil spills and enhance chemical reactions. Every day, most people come in contact with a clay mineral in some form or other.

How I Became Interested in Clays

"When I was little I was always playing in the dirt and mud and I liked the way the wet mud felt when you would squeeze it with your fingers and toes. When I got older, I spent a lot of time hiking and camping, particularly in the Southwest. I began to notice that the sand and mud was different in different places. Why is beach sand white and the sand in the Painted Desert red, green and yellow? Why does some mud get slippery when it's wet and dry into a hard surface like concrete? As I later learned when I studied geology, all of these observations are the common properties of sand and clay that make up the sandstones and mudstones that we see everywhere, and that fill most sedimentary basins. Studying these rocks and the clay minerals that are contained in them is a fascinating branch of geological research."