Diamond
From GeoClasses
Whats a Carat?
A carat is not the same as a karat of Gold! Carat is also not the same thing as a carrot which is the vegetable most favored by a rabbit.
One metric carat is equal to 200mg. This is just another way of expressing the weight of the diamond. Back in the day traders had to find a standard in which they could express the weight of a precious gem such as diamond. Wheat seeds was a common trade item that had a very uniform size and weight. Due these properties early traders used wheat seeds as a standard for precious gem weight.
One karat is one part Gold. Pure Gold is 24 karats. If a Gold ring is 14 karats then it is 14 part Gold and 10 part of other metals.
14 carats of a Diamond is 2800mg of Diamond. These two terms are often confused because of the similarity in spelling and pronunciation.
What is a Diamond and how do they form?
Ferris Bueller: "Cameron's so tight, that if you stuck a lump of coal up his [butt], in 2 weeks it would turn into a diamond."
Although Ferris Bueller is on the right track the pressure required for the formation of diamonds is a bit more than what a human gluteus maximus can offer. Diamonds do indeed require pressure and also a great amount of heat in order to shape it to its final form. It takes around 435,113 PSI (pounds per square inch) and about 400 Degrees Celsius (752 Fahrenheit) at 161km below the surface of the Earth for Carbon to transform into Diamonds. If any of these conditions are not met Graphite is formed instead.
Diamonds are usually formed around the Earth's cratons. Cratons are very old and geologically inactive crusts. Since they see little geological activity they run very deep into the Mantle. Diamonds do not come to the surface of the Earth by themselves. Kimberlite or lamproite are young volcanic rocks that are the carriers of diamonds. Volcanic activities around these cratons allows the magma to transport kimberlite or lamproite volcanic rocks from deep beneath the crust. These volcanic rocks then form a 'pipe' due to its pipe-like shape called kimberlite or lamproite pipes.
Crashing meteorites can also cause the creation of diamonds. The pressures and the high temperatures associated with the meteorite impact can easily transform carbon into diamond structure. The diamonds created by these meteorites are usually no larger than one centimeter in diameter.
The above illustration shows the necessary pressure, temperature, and depth required for diamond formation.
Graphite has a hexagonal sheet structure. It is very electrically conductive along its sheets. Additionally Graphite can be used as a dry lubrication material due to its sheet structure allowing the different sheets to slide along each other with very little friction.
Diamond however has a cubic crystal structure. There are no sheets of carbon atoms and all the atoms are bonded to each other uniformly. This gives diamond its toughness. Diamond is a rather poor electrical conductor with the exception of certain blue diamonds that are used for doping semiconductors. Additionally a natural diamond is one of the best heat conductors in the world. The reason why its not used on every computer's heatsink is due to the high cost. Man made diamonds are comparably less thermal conductive than natural diamonds. Despite being lower in relative cost to natural diamonds man made diamonds are still priced high enough to make it impractical to be used for, say, building heatsinks.
How hard is a Diamond?
Mineralogist Frederich Mohs created a scale to chart the relative hardness of various minerals.
The scale below shows how easily a mineral can be scratched by other minerals. As you go down the chart the minerals become increasing resistant to scratching that would of easily affected the minerals above it. Notice how Diamond can cut the minerals directly above it but nothing on that chart can cut diamond except for diamond itself.
Here is another representation of the same scale. This scale ranges from 1 to 10 with 10 being the hardest material.
