SRAC Presents: Mineralogy for Kids

Rare Rocks: In this episode, Ted Keir tells us about three less ordinary rocks.

Manganese Nodules - Concentrations of manganese nodules can be found found on the floors of many oceans, but are hard to get because of the depths at which they are found. Marine manganese nodules from certain regions are significantly enriched in nickel, copper, cobalt, zinc, molybdenum, and other elements so as to make them important reserves for these strategic metals.

Fulgurites -When a bolt of lightning strikes a sandy surface, the electricity can melt the sand. This melted substance combines with other materials. Then it hardens into lumps of glass called fulgurites. (Fulgur is the Latin word for lightning.)

Gastroliths (Dinosaur Gizzards)- Rock fragments were swallowed to assist in the grinding process in the dinosaur digestive tract, much as some birds now swallow grit and pebbles to grind food in their crop. Once the animal has decayed, smooth round stones remain – often the only clue to their past use is the fact that they are geologically different from the surrounding rocks in the region.

Stalactites and Stalagmites - Deposits in limestone caverns form stalactites and stalagmites by the evaporation of waters bearing calcium carbonate. Stalactites grow down from the roofs of caves and tend to be long and thin, with hollow cores. The water moves down the core and precipitates at the bottom, slowly extending the length while keeping the core open for more water to move down. Stalagmites grow from the floor up and are commonly found beneath stalactites; they are formed from the evaporation of the same drip of water that forms the stalactites.

Rare Rocks         Manganese Nodule