DIAMONDS ARE FOREVER

The Origin of Diamonds 

Diamonds are just carbon in its most concentrated form

Temperatures can reach 1,652 F (900 C) in Archean cratons. These are common places for diamonds to form. Archean cratons are stable, horizontal geological formations created billions of years ago that have been unaffected by major tectonic events, according to Rex Diamond Mining Corp. These cratons are found in the center of most of the seven continents (most tectonic activity takes place around the edges). 

 Diamonds form about 100 miles (161 km) below the Earth's surface, in the molten rock of the Earth's mantle, which provides the right amounts of pressure and heat to transform carbon into a diamond. In order for a diamond to be created, carbon must be placed under at least 435,113 pounds per square inch (psi or 30 kilobars) of pressure at a temperature of at least 752 degrees Fahrenheit (400 Celsius). If conditions drop below either of these two points, graphite will be created. At depths of 93 miles (150 km) or more, pressure builds to about 725,189 psi (50 kilobars) and heat can exceed 2,192 F (1,200 C).

Most diamonds that we see today were formed millions (if not billions) of years ago. Powerful magma eruptions brought the diamonds to the surface, creating kimberlite pipes

Kimberlite pipes are created as magma flows through deep fractures in the Earth. The magma inside the kimberlite pipes acts like an elevator, pushing the diamonds and other rocks and minerals through the mantle and crust in just a few hours. These eruptions were short, but many times more powerful than volcanic eruptions that happen today. The magma in these eruptions originated at depths three times deeper than the magma source for volcanoes

The magma eventually cooled inside these kimberlite pipes, leaving behind conical veins of kimberlite rock that contain diamonds. Kimberlite is a bluish rock that diamond miners look for when seeking out new diamond deposits. The surface area of diamond-bearing kimberlite pipes ranges from 2 to 146 hectares (5 to 361 acres

Diamonds may also be found in river beds, which are called alluvial diamond sites. These are diamonds that originate in kimberlite pipes, but get moved by geological activity. Glaciers and water can also move diamonds thousands of miles from their original location. Today, most diamonds are found in Australia, Borneo, Brazil, Russia and several African countries, including South Africa and Zaire.

Diamond Properties

diamonds are the crystallized form of carbon created under extreme heat and pressure.  A diamond ranks a 10 on the Mohs Hardness Scale (see below). It can be anywhere from 10 to hundreds of times harder than a mineral ranked nine on the Mohs scale, such as corundum. Corundum is a class of minerals that includes rubies and sapphires

Diamonds are made of carbon atoms linked together in a lattice structure. Each carbon atom shares electrons with four other carbon atoms, forming a tetrahedral unit. This tetrahedral bonding of five carbons forms an incredibly strong molecule. Graphite, another form of carbon, isn't as strong as diamond because the carbon atoms in graphite link together in rings, where each atom is only linked to one other atom.

Cutting Diamonds

There are special techniques that are used to cut and shape a diamond before it gets to the jewelry store. Diamond cutting creates the facets that you see in the diagram above. Diamond cutters use these four basic techniques:

• Cleaving - In order to remove any impurities or irregularities in the diamond, a rough diamond is placed in quick-drying cement. A sharp groove is then carved into the diamond, using another diamond or a laser, along planes of weakness. Then, a steel blade is placed in the groove and a sharp blow to the blade splits the stone. It is then removed from the cement.
• Sawing - Sometimes, diamonds have to be cut against a cleavage plane, which cannot be done with cleaving. Using a phosphor-bronze blade rotating at about 15,000 rpm, the saw slowly cuts through the diamond. Lasers are also being used to saw diamonds.
• Bruting - The diamond is placed in a lathe, and another diamond in the lathe is rubbed against it to create the rough finish of the girdle, the outside rim of the diamond at the point of largest diameter.
• Polishing - To give the diamond its finished look, it is placed onto the arm above a rotating polishing wheel. The wheel is coated with diamond powder that smoothes the diamond as it is pressed against the wheel.

 

Rating Diamonds

Diamonds are judged on several factors that determine their beauty. Most diamonds never reach the consumer market because they are too flawed. Often, these diamonds are used for industrial purposes -- as an abrasive, for drill bits or for cutting diamonds and other gems. If you've ever purchased a diamond, you've heard of the "4 Cs:"

• Cut - This refers to how the diamond has been cut and its geometric proportions. When a diamond is cut, facets are created and the diamond's finished shape is determined.
• Clarity - This is the measurement of a diamond's flaws, or inclusions that are seen in the diamond. Clarity levels begin with Flawless and move down to Very Very Slight (VVS), Very Slight (VS) and Slightly Included (SI).
• Carat - This is the weight of a diamond. One carat is equal to about 200 milligrams.
• Color - In referring to transparent diamonds, the color scale runs from D to Z, beginning with Icy White -- the color of the most expensive diamonds -- and ending with a light yellow.

Other unique qualities of the diamond include its transparency, luster and dispersion of light. A diamond that is created from 100-percent carbon will be completely transparent. Diamonds often contain other elements that can affect the color. Although we often think of diamonds as being clear, there are also blue, red, black, pale green, pink and violet diamonds. These colored diamonds are the truly rare ones.

The Mohs Scale

The Mohs Scale is used to determine the hardness of solids, especially minerals. It is named after the German mineralogist Friedrich Mohs. The scale reads as follows, from softest to hardest:

• Talc - easily scratched by the fingernail
• Gypsum - just scratched by the fingernail
• Calcite - scratches and is scratched by a copper coin
• Fluorite - not scratched by a copper coin and does not scratch glass
• Apatite - just scratches glass and is easily scratched by a knife
• Orthoclase - easily scratches glass and is just scratched by a file
• Quartz (amethyst, citrine, tiger's-eye, aventurine) - not scratched by a file
• Topaz - scratched only by corundum and diamond
• Corundum (sapphires and rubies) - scratched only by diamond
• Diamond - scratched only by another diamond

Source: Kingzett's Chemical Encyc.

 

 

Natural colored diamonds are formed in the same way as white diamonds with the only difference being the color of the crystal. The color is believed to have occurred in the forming of the crystal millions of years ago by nitrogen or other elements being trapped in the crystal lattice. Natural colored diamonds come in all shades, hues and colors of the rainbow, with the most common and inexpensive colors ranging from brown to yellow.

 Pink diamonds are one of the rarest and most treasured colors commanding some of the highest prices per carat ever paid

4  Cs Of DIAMONDS

"4 Cs" -- cut, clarity, carat and color