Diamonds Are Forever
Diamonds are still a girl's best friend, right? We love the
shiny gems. They are the most popular rocks sold today. But what
exactly are they, anyway? Where do they come from? What else are
they used for?
Diamonds are a mineral in one of the two crystalline forms of
the element carbon. They are the hardest natural substance man
knows. Diamonds are sold as gems, and used in industrial
applications for smoothing, cutting, and polishing hard
materials.
Diamonds are most famous for crystallizing in the common
colorless form. They may also be tranlucent to transparent
white, yellow, green, blue, or brown. Diamonds have a high
refractive index which is why they are so brilliant and sparkly
after cutting. The familiar shape of the diamond is the
octahedron.
The most brilliant diamonds become gemstones for jewelry and
other uses. For those that don't make it to gems, there are
other options. There is bort, which is a more poorly
crystallized or undesirable color and in fragmentary condition,
and carbonados which is gray to black opaque. Bort and
carbonados are used as abrasives for the cutting of diamonds and
the cutting heads of industrial rock drills.
Diamonds are found in alluvial formations and in volcanic pipes,
filled for most of their length with blue ground or kimberlite,
and igneous rock consisting primarily of serpentine. Diamond
yielding earth is mined by both the open-pit method and by
underground mining. After removal to the surface, the soil is
crushed and concentrated. Passing the concentrated material in a
stream of water over greased tables does the needed sorting. The
diamond is largely water repellent and sticks to the grease and
the other minerals retain a film of water, which prevents the
sticking to the grease. Then the diamonds are removed from the
grease, cleaned, and graded for sale and use.
The earliest sources of gem diamonds were India and Borneo. Some
famous diamonds are the Great Mogul, Regent, and Pitt. Other
famous diamonds include the Hope (blue), Dresden (green) and
Tiffany (yellow). In the early 18th century, deposits similar to
those in India were found in Brazil, mainly of carbonados. In
1867 a stone found in South Africa was recognized as a diamond.
Within a few years began a wild search for diamonds. In
1870-1871, dry diggings including most of the celebrated mines
were discovered.
Synthetic diamonds were successfully produced in 1955; a number
of small crystals were produced when pure graphite mixed with a
catalyst was subjected to pressure of about 1 million lb per sq
in. and temperature of the order of 5,000-F (3,000-C). Synthetic
diamonds now are extensively used for industry, mainly due to
the ease of obtaining and lower cost for them. Diamonds are
still very popular and symbolize many things. Their popularity
does not seem to be dwindling any time in the near future.