Geology MW 7:45
Extra Credit
Diamonds are a Girl’s Best Friend A diamond is considered to be one of the most precious and rare stones on earth. These stones “are rare for three reasons: they form deep within the Earth in very localized places beneath continents, an extremely unusual kind of volcanic activity is needed to bring [diamonds] to the surface, and only about 20 per cent of them are gem quality” (Fleet, Hart, Wall 23). Not all diamonds are good enough to sell for jewelry purposes but are good for different industrial uses. Many extensive geological processes are involved in the formation of diamonds as well as long periods of time needed. “Diamonds which are mined formed about three billion years ago” (Fleet, Hart, Wall 23). The processes that occur in diamond formation are not completely known but different geologic evidence indicates certain processes that have taken place. Most areas that contain a significant amount of diamonds are older areas within the earth’s crust containing magmatic basaltic rocks. Diamonds are mostly found in kimberlite pipes. A kimberlite forms in the mantle within the earth along with a substantial amount of volatiles. A “free carbon system” is also an essential need in the formation of diamonds. Between the extreme temperature and pressure along with the volatiles (possibly water and carbon dioxide), the magma pushes upward and forms a pipe that is compared in shape to a carrot. The actual pipe forms in that process. This is a rare type of volcanic explosion that no person has ever seen, but can be seen in geologic history. Also a kimberlite pipe is a type of diatreme, which is another type of pipe filled with breccias from a gaseous explosion. A kimberlite rock formed in the mantle of the earth and can reach temperatures up to 900 degrees Celsius (Pokhilenko 28-29). For diamonds to come up to the surface via kimberlite pipes, they have to be “tectonically activated” and the pipe will