Diamonds are important for several reasons, and not just for gifts and the like. Geologists can use inclusions (tiny specks that appear most diamonds) to tell a great deal about the mantle and other pieces of rock. The ironic part here is that gem buyers try to stay away from often unattractive inclusions in their diamonds, while geologists flock to try to find more and more inclusions in their diamonds. One might wonder what the geologists' wives think about that?

Diamonds, as we have learned, are very old. Being among the oldest gems (sometimes more than three billion years old), geologists can use these inclusions to look at these ancient mantle samples. Lots of data can be extracted from modern tools. One thing that scientists have learned from this is that kimberlites and lamproites come from ancient seafloors according to Andrew Alden from The Diamond Zone (http://geology.about.com/library/weekly/aa021598.htm). This tells us that the pieces of the ocean crust from two to three billion years ago that subducted beneath the continents have been there for over a billion years. Alden states that another piece of data obtained from this is that the seafloor has been subducting beneath the continents for nearly as far back as we can tell. However, diamond pipes are so rare that all subducted crust is probably digested into the mantle. These findings are very interesting to geologists and pose many questions about how plate tectonics might work.