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As vintge vixen Marilyn Monroe sang, diamonds are a girl's best friend. They've come to symbolize the height of affluance and affection. Through the baubles have been in vogue only since the 1950s, these minerals have existed deep inside the Earth for biliions of years. And while they aren't any rarer than rubies, emeralds or sapphires, diamonds' unique properties put them a cut above the rest.

Diamond is the most concentrated form of pure carbon in the natural world and the strongest mineral on Earth, far exceeding other carbon allotropes such as graphite and fullerite. The secret to diamond's superior strength is found on the molecular level. Carbon atoms possess four valence electrons forms a covalent bond with a valence electron of a neighboring carbon atom. Since all of the free electrons are bonded uniformly, it creates a rigid tetrahedral lattice that gives the coveetd mineral its prized properties.

The organic process of diamond formation requires four key ingredients: carbon, pressure, heat and time. When it comes to heat and pressure, the specific conditions are at least 752 degrees Fahrenheit (400 degrees Celsius) and 434,113 pounds per square inch (30 kilobars). Prime diamond real estate is located about 100 miles (160 kilometers) underground in the Earth's mantle. There, diamonds have formed over billions of years from heated and pressurized carbon.

Hundreds of millions of years ago, eruption of magma from the mantle propelled natural diamonds closer to the Earth's surface. The funnel-shaped areas carved out by the magma eruptions are called kimberlite pipes, named for the first formation discovered in Kimberley, South Africa. Gradually, the tops of the pipes eroded, exposing the diamonds below. Erosion can also carry diamonds from their oroginal location into riverbeds and coastal lands. In its roughest form, diamond ore doesn't look like the shiny nuggets atop engagement rings. Diamonds must be sorted, cut and polished to bring out their luster. 

Which paragraph tells you about how diamond come to the earths' surface?