THE DIAMOND STATE? Everyone knows there's oil in North Dakota, but diamonds? Perhaps. It was reported last week that an international company had drilled a hole near St. Thomas in a search for diamonds. Geologists say rock formations in eastern North Dakota resemble those in diamond-producing parts of nearby Canada. The company said it was searching for kimberlites, or molten rock from ancient volcanoes where diamonds could occur. After not finding any, the company said the project was not encouraging enough to continue, although company officials said that doesn't mean they believe finding diamonds in the state is impossible. It certainly is an interesting proposition. Perhaps someday North Dakota will be known as home to diamonds as well as black gold.