Diamond

Mineral Name: Diamond

Chemical Composition: Carbon (C)

Color: Colorless, yellow, brown, gray and black. Some diamonds are lightly tinted with yellow, brown or orange. Occasionally they will be blue, pink, purple, red, and orange.

Streak: White

Hardness: 10

Cleavage/Fracture: The cleavage present in a diamond can be described as octahedral, it has four perfect planes that create a octahedron. These are very easy to spot and do not leave the observer to question the geometry. (1)

Crystal Form: The crystal form that the diamond is commonly seen in is an octahedral, with some rare cases of dodecahedral (12 seperate faces) and hexoctahedral (48 equal triangular faces) (9). The most rare type of diamond form is a cube. Crystals growth layers that can be seen in diamonds can be complicated triangular patterns known as trigons (2). Trigons are little triangular extrusions on rough diamonds that can naturally occur. The triangular patterns can be fragmented or clean, depending on the curved faces. The last crystal form that a diamond can take is a ball-shaped development that is larger in structure (1). (11).

Luster: Diamonds are mostly described as adamantine because of its transparent and shiny nature (2).

Special Features: Diamonds are the hardest known natural mineral on Earth (1). At 7362° degrees Fahrenheit, the diamond has the highest melting point of any natural mineral (1).

Varieties: There are many varieties of diamonds, mostly relating to the different colors and purity when they are formed. The ideal diamond is colorless; they are the most expensive and rare type. Diamonds will have a yellowish tint as they slowly become more impure. Most diamonds cannot be identified with a yellow tint with the naked eye (3). Other varieties of diamonds include white, blue, red, and green, these colored diamonds are extremely rare. These colored diamonds are known as Fancy diamonds.

Other diamond types include, lonsdaleite, carbonado, bort, and ballas. A Lonsdaleite diamond is created from great heat and stress to form a polymorphed hexagonal diamond. Carbonado is a black opaque diamond that has a specific gravity of 3.1-3.3 exhibits no cleavage. Bort diamonds are considered gem quality and have imperfect crystals that appear as a darker color. Lastly, ballas diamonds have an internal radiating structure, separating them from other varieties (1).

Mineral Group: Diamonds are made up of only carbon, so diamonds can be considered to be in the native elements group. These minerals contain in their molecular structure only one element (17).

Environment: Natural diamonds are formed by extremely high pressure and temperature. Only limited zones in the Earth's mantle are able produce diamonds. These locations occur where temperatures of 2000 degrees fahrenheit are found as well as a depth of 90 miles below the surface (4). Diamond stability zones are formed by volcanic explosions deep in the Earth's mantle, erupting through a feature called a Kimberlite Tube. They also can be formed in a subduction zone, with less extreme depth and temperature but an extremely high amount of pressure. Subduction zone diamonds tend to be smaller sized diamonds. Another formation area can be on asteroid impact sites, although this is extremely rare (4). Also, with new technology, industrial diamonds are made in a lab with large amounts of electricity to generate the heat and pressure needed (4). Diamonds can also be found in placer deposits, which are less sought after but have recently become more popular (13). Placer deposits are formed when minerals erode from the rock and then become part of the sediment (12).

Associated Rock types: Diamonds are conjoined and then brought to the surface by Kimberlite, which is a gas-rich potassic igneous ultramafic rock (5). Lamproite is another rock associated with diamond, and this rock is ultra-rich in potassium and formed from volcanic and sub-volcanic rock (13).

Occurrence in North America and the World: Kimberlite deposits in which diamonds are found are distributed from the midwest going towards the eastern part of the United States. There are large formations in the middle of the South American Continent, and large groups of diamonds are mined in southern Africa. A small concentration is also present near the northern tip of Asia. Small amounts of diamonds are found in China and Australia and nearly non-existent in Europe and Northern Africa (6).

Economic: Diamonds are a huge money making export for Canada and Africa, especially Botswana, since diamond export makes up one third of their GDP (10). Diamonds are generally used for jewelry and decoration since they don’t deteriorate and can be passed from generation to generation in families without showing wear (1). They are cut and shaped in the typical triangular-faced pattern that are seen in rings. Faceting a diamond in this way brings out the crystalline-pattern more clearly, making them more appealing to the consumers. Diamonds can also be used in drill bits for mining even more diamonds and increasing economic wealth (9).

Industrial Uses: Diamonds are used a lot in the music industry. They are used primarily for improving the quality of the sound being dispersed from speakers and record players. There are diamond-tipped needles that sit on records that don’t degrade, meaning there is no need for purchasing new needles. With an increase resistance to decay and greater hardness, the needle of the record player can be more fine, allowing for it to read into the grooves to create a more pure and exact sound (14).

Diamonds are also used in the absorbing or or transmitting heat. Diamonds have the highest thermal conductivity of any known material. More specifically, diamond can be used to draw heat away from heat sensitive electronics (9). Diamonds are put used inside computers in places that have to be able to withstand a great amount of heat, preventing electronic overheating as diamond absorbs the heat.

Diamonds are also used in the fabrication industry for cutting metallic materials, one example being cutting metallic materials while making cars. Because diamond is the hardest material, they can be used to cut a multitude of very hard materials. Particles of diamond are placed into blades and other cutting tools to increase both sharpness and durability. Another method of applying a diamond to a cutting edge is changing it into a dust particles. These particles are then applied to the utensil and allow for a much sharper finish, this is mostly used for cutting other diamonds (4).

First Notable Identification: The first notable and historical appearance of diamonds comes in the late 4th century B.C.E. in India. Also named, “vajra” or thunderbolt, the diamond played an important part in scriptures from Hinduism (7). Also, Sanskrit manuscripts were found describing this mineral by a minister from a northern Indian dynasty (7).

How We Identified It: Diamonds are formed like and can resemble many different crystals but what sets diamonds apart from everything else is the hardness of a diamond. The hardness level for a diamond is a level 10. That makes the diamond the toughest mineral and you can scratch any other mineral with a diamond.

Don’t Confuse It With: Moissanite is most commonly confused with diamonds. The hardness level is a 9, which is not that far off from a diamond when tested. They both have similar colors but moissanite becomes more colorless as it gets smaller. Although, when moissanite has a light shined on it, it shows a yellow or green hue (8). Another mineral that it can be confused with is zircon, it has a gemstone look and normally forms in the same pattern (triangular faces) as that of a diamond but it is softer (16). Lastly, The Herkimer Diamond, which takes its name from having the appearance of a diamond, is actually just a quartz crystal and softer (15).