Diamonds and their Origin

Sheets of pluton can be parallel to or angled with respect to the sedimentary rock around it. A sill will be parallel to the layers, while a dyke is discordant or angled with respect to the layers. Sills tend to creep in between layers, while dykes push up underneath to form some type of non-horizontal section of magma. A laccolith is a very thick sill that created such a thick layer that it deformed the rock above it. A pipe is any cylindrical place where magma shifts from one place to another. Pipes can connect different plutons to one another.

DIAMONDS AND THEIR ORIGIN

Diamonds are not made from coal as many people think. Coal comes from the carbon you see in land plants and most diamonds on earth predate that time period, so the idea that they come from coal is not feasible. Diamonds are made from carbon but unlike coal, they come from vertical magma pipes and not horizontal layers. Coal forms much more superficially than diamonds as well. So, how do diamonds form?

Diamonds we use commercially now come from very deep volcanoes emitting magma from deep within the earth. The magma comes up quickly, passing through the zone where diamonds are stable, ejecting xenoliths that contain diamonds. This zone where diamonds are held within the earth is called the diamond stability zone.

Open-pit mines also allow for diamond collection because they are found in sedimentary rocks that are in rocks or streams. They were once formed about 90 miles below the earth where the temperatures are high – 2000 degrees Fahrenheit. Now you have both pressure and temperature needed to make diamonds. Plates where the continents are most stable have these diamonds in them. These are the mid-continental plate areas. Don't expect to find large diamonds anywhere, but you might get lucky.

Where did all this carbon come from? It was carbon that was trapped within the earth at the time it was formed and never when plants were on earth. They may have gone deeper in some areas due to subduction of mantle into the magic sweet spot where diamonds are made. Surprisingly, diamonds can come from asteroids that have impacted the earth with enough force to create diamonds. Again, pressure and heat make diamonds. These are very rare sources of diamonds, however.

Diamonds used in things like manufacturing and cutting tools are sometimes artificially made – simply by having heat and pressure create these tiny diamonds for industrial use. These lab-created diamonds mean we don't have to find and use those gotten from the earth to make a large number of them.