GO 340 Gemstones & Gemology

Emporia State University
Susan Ward Aber

academic.emporia.edu/abersusa/go340/diamond.htm

Everything You Always Wanted to
Know About Diamond

Just the Facts...


Image taken from
The Image Gallery
Diamonds.
Diamond, composed of carbon, is the hardest natural substance in the world. Each carbon atom is surrounded by four neighboring carbon atoms in a tetrahedral coordination that is the result of a covalent bond and a face-centered arrangement in the cubic unit cell. Diamond is in the isometric crystal system, which is reflected in the commonly found octahedral or cubic crystal form. The external crystal class is 4/mBar32/m, while the space group designation is F41dBar32/m. Twins are common on the {111} plane. It has perfect four directional cleavage, adamantine luster, and both a high refractive index, 2.42, and specific gravity, 3.52. Color is usually pale yellow to colorless, but can also be brown, blue, green, orange, red, and black.
Diamond may be up to 3 billion years old, which is much older than their surface host rock (Harlow, 1998, p. 60). Diamond crystallization originates some 200 kilometers, or 320 miles, beneath the surface and the disaggregated crystals are merely transported to the surface via kimberlite and lamproite pipes (Harlow, 1998, p. 54). These igneous host rock formations are roughly cylindrical in shape and act as a conduit from the Earth's mantle to the contintental crust.

Diamonds are differentiated between various types, Ia, Ib, IIa, and IIb. Although this information is important to the diamond cutter, it is of no value to the student merely interested in diamond as a gemstone. Diamond's superior optical properties and hardness has earned this mineral the highest respect in both industry and jewelry. It has a long tradition of invincibility and hence the Greek name, adamas.

An excellent source of diamond information can be found at http://www.diamond.info/. Another good fact source is found at the Molecule of the Month, http://www.bris.ac.uk/Depts/Chemistry/MOTM/diamond/diamond.htm (Paul May, University of Bristol, U.K.). Finally, Farlang Gem and Diamond Foundation, www.farlang.com, has an online library of resources on the history of geology, gemology, and mining at www.farlang.com/gemstones-diamonds-books, with specific diamond references at www.farlang.com/diamonds-references. These websites are well worth a visit.


Image taken from
a former site at
adiamondisforever.com,
sponsored by The
Diamond Trading Company

Beyond the Facts...


Image taken from
a former site at
adiamondisforever.com,
sponsored by The
Diamond Trading Company
Individuals and societies have ascribed diamond's important status with both symbolism and as a scientific curiosity with industrial value. Therefore, both scientist and laity find diamond fascinating because of the dual nature of scientific-industrial practicality and romantic ethereality created through traditions and advertising. The origin of dimaond may have been uncovered in the twentieth century, but appreciation for diamond has been known since diamond discovery in India, prior to 400 B.C.E.1 (Harlow, 1998, p. 118). Historically, diamond has been referred to as the essence of purity and invincibility, a symbol of royalty, and token of everlasting love (p. 1). Diamond is the birthstone for April.

Visit the Diamonds at the Paris Natural History Museum webpage, http://www.mnhn.fr/expo/diamants/index/english/ukinfo.htm#peintures, to find out about how diamonds have been portrayed in paintings from court portraits in the 15th century to information on the French Crown Jewels. The Beau Sancy, a 40 carat diamond in the French crown jewels, is depicted in Marie de Medicis's crown, a painting at the Louvre.

Today, 75-80% of the world's natural diamonds are used for industrial purposes and 20-25% for gemstones. It is the chemical and physical properties of this mineral that give it the superior cutting ability for industrial use. Diamond coatings have improved on diamond's industrial applications in cutting and in aiding the performance of semiconductors. It is the optical properties of this mineral that give it the superior beauty and durability to be used as a gemstone. The rarity of this gemstone is related to the petrogenesis of the igneous rock in which the diamond is recovered. Diamond may even be found in meteorites. It is an important economic resource, responsible for developing nations and creating war. Faceting diamond, in order to maximize its optical properties, depends upon a knowledge of geometry. Diamond is the perfect mineral to focus on considering its notoriety and the fact that diamond studies cross disciplines, such as mineralogy, geology, astronomy, material science, mathematics, anthropology, art, history, and economics. Follow up on one such interesting focus, the importance of diamond coatings to a past war, at http://www.cnn.com/TECH/9610/08/t_t/diamonds/index.html.

The Hope Diamond, shown in the image to the right, has a long and colorful history. To read about this deep blue stone, visit

  • mineralsciences.si.edu/hope.htm
  • http://www.smithsonianeducation.org/students/
    secrets_of_the_Smithsonian/history_hope_diamond.html
  • http://history1900s.about.com/library/weekly/aa071300a.htm,
    The Curse of the Hope Diamond at About.com, 20th Century History.

    Another diamond article can be viewed at the Smithsonian website, mineralsciences.si.edu/collections/napoleonnecklace.htm, regarding a comprehensive research report on the Napoleon Diamond necklance. Another special diamond is found in the Iranian Crown Jewels, the Darya-i-Nur. This is one of the oldest faceted diamonds, believed to have been in the collection of the first Mogul emperor of India (Gaal, 1977, p. 68). It is 176 carats, a pale pink color, and mounted in a setting with four rubies and 467 diamonds (p. 68). Visit the Wikipedia sites for more information, en.wikipedia.org/wiki/Imperial_Crown_Jewels_of_Persia or en.wikipedia.org/wiki/Daria-i-Noor.


  • The deep blue Hope
    diamond is located in
    the Smithsonian,
    Washington, DC. Image
    taken from a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    Fact or Fiction: Exploring The Nature of Diamonds

    In addition to the excellent coverage of diamond in your required textbook, many web sites exist to further your cyberknowledge of diamonds! The Nature of Diamonds, from the American Museum of Natural History, adiamondisforever.com, from the Diamond Trading Company, are among the many good overview sites on diamond. The Fact or Fiction presentation below will rely upon these web sites and others to enhance your understanding of diamond.

    Statistics  *  Occurrences  *  History & Mining

    Industry & Technology  *  Conflict Diamonds  *  Evaluate


    Diamond Statistics

    Fact or Fiction?!?

    1. Although diamonds vary from colorless to black, most are tinged with yellow. Diamonds are often set in yellow gold to mask the yellow body color. Nitrogen is believed to be responsible for diamond's yellow color and blue diamonds are colored by boron. Carbon is adjacent to nitrogen and boron in the periodic table and substitution is possible because of size similarity of the elements.

    This is a fact.

    For more information, visit these external sites:


    Fact or Fiction?!?

    2. Diamond has a scratch hardness of 10 on the Mohs scale and therefore it is indestructible.

    This is fiction! In addition to good cleavage, diamond can be scratched by diamond!

    For more information, visit this external site:


    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    3. Diamond often fluoresces blue and hence the historical "blue-white" color designation given to colorless diamonds. Other fluorescent colors include orange and sometimes a bright yellowish-green.

    Fact or Fiction!?! This is a fact.

    For more information, visit this external site:

  • truth about Diamonds, on fluorescence, http://www.diamonds.pro/truth-about/diamond-fluorescence/


    4. Diamond disperses light well resulting in a balanced fire, which is due to included water.

    Fact or Fiction?!? This is fiction! Included water helps to give opal a play-of-colors, but is not related to the dispersion of diamond.

    For more information, visit this external site:

  • NOVA on What Makes a Diamond Sparkle, http://www.pbs.org/wgbh/nova/physics/diamond-science.html


    5. Diamond's high refractive index gives it extraordinary brilliance, scintillation (sparkle), and adamantine luster. When choosing smaller diamonds, brilliance is the key factor.

    Fact or Fiction?!? This is a fact.

    For more information, visit these external sites:

  • Why do diamonds shine? http://physics.stackexchange.com/questions/43361/why-do-diamonds-shine
  • Reflection and refraction of light in diamond, http://www.youtube.com/watch?v=kYnNe-esGvc


  • Image taken from
    Dendritics


    6. Diamond jewelry is a meaningful gift that should never be removed for cleaning.

    Fact or Fiction!?! This is fiction! Although gifts are often meaningful, diamond has an affinity for grease! This is helpful in separating mined diamond but detrimental to keeping your diamond ring clean after washing greasy dishes, pots, and pans.

    For more information, visit these external sites:



    Photo date 5/2000 © S.W. Aber
    7. This diamond testing instrument (left) measures thermal conductivity to separate diamond from look alikes. Not only is diamond's thermal conductivity higher than other colorless gems, it is four times greater than copper!

    Fact or Fiction!?! This is a fact.

    This instrument has limitations though and does not recognize some rare natural diamonds. While most gem diamonds have high thermal conductivity, some diamonds and most diamond imitators do not. Type IIb diamonds are semi-conductors and as such are electron acceptors, not donors. This limitation in detecting thermal inertia extends also to blue diamonds that contain the impurity boron, which is responsible for the blue color in the Hope Diamond for example; these natural diamonds may register incorrectly as not diamond using this thermal conductivity device.

    For more information, visit:

  • Paul May's Diamond website explaining the different types and properties of diamond, www.bris.ac.uk/Depts/Chemistry/MOTM/diamond/diamond.htm
  • Thermal Conductivity of Diamond http://www.diamond-materials.com/EN/cvd_diamond/thermal_properties.htm and http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thrcn.html


  • Occurrences

    8. When prospecting for diamond, good indicator minerals are red garnet and olivine.

    Fact or Fiction!?! This is a fact.

    For more information, visit these external sites:


    9. Primary deposits of diamond are only found in the intrusive, igneous rock type called kimberlite.

    Fact or Fiction!?! This is fiction! Diamond is also found in lamproite deposits.

    For more information, visit:


    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    10. Inclusions are helpful to identify the rock within which diamonds formed and the age of the diamond. Although inclusions include garnet and diopside, the most common inclusion in diamond is diamond.

    Fact or Fiction!?! This is a fact.

    For more information, visit:


    History and Mining

    11. Extensive mining of diamonds shifted from India (17th century), to Brazil (18th century), to the African continent (19th century), and finally Australia and Canada (20th century). Today diamonds are mined in some 25 countries on every continent but Europe and Antarctica. The top seven producing countries, that account for 80 percent of the world's rough diamond supply, are Australia, Botswana, Zaire, South Africa, Russia, Angola, and Namibia.

    Fact or Fiction!?! This is a fact.

    For more information, visit DeBeers:


    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company


    12. Barney Barnato founded DeBeers Consolidated Mines by purchasing other prospector's diamond claims and became the leader of Rhodesia (now Zimbabwe).

    Fact or Fiction!?! This is fiction! Although Barnato was one of the first to consolidate mining claims, Cecil Rhodes founded De Beers. De Beers sells gem diamonds through sightholders and you can learn more about this process below.

    For more information, visit:

  • Emerling, S. (2000). Not Forever. Salon on the death of Harry Oppenheimer and the DeBeers Cartel. http://archive.salon.com/business/feature/2000/09/27/diamonds/print.html


    13. Diamonds are found in three types of deposits: alluvial gravels, glacial tills, and kimberlite or lamproite pipes.

    Fact or Fiction!?! This is a fact.

    For more information, visit American Museum of Natural History on:


  • Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company


    Industry & Technology


    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company
    14. Over 75% of the mined diamonds go to industry each year, with such applications from windows to phonograph needles!

    Fact or Fiction!?! This is a fact.

    For more information, visit:


    Conflict Diamonds

    16. The diamond industry is to blame for war in Africa.

    Fact or Fiction!?! This is fiction! Africa is rampant with political, social, and economic corruption, which is behind wars in Africa. Some have blamed the diamond industry for fueling these struggles because the sale of diamond is one way in which madmen and terrorists raise the money to buy weapons. On other continents, illegal drug trafficking and oil monies finance conflicts. Placing the blame for war on the diamond industry is unfair for African diamond producers as well as the diamond industry in non-war areas.

    The diamond industry faces a most difficult challenge to continue legitimate business in African mining and cutting plants, while ensuring that monies do not fund rebel armies. In an effort to police the international diamond industry, UN resolutions to US legislation have been offered and debated, but there is never an easy solution to war or greed. Illiteracy and a lack of a broader communication network inhibit human rights progress for the peoples of third world countries. Poverty and over population stress humanity worldwide. It will take a greater global effort than any one industry or government could shoulder to dictate and regulate morality in all cultures and therefore alleviate ignorance and war.

    The diamond industry is not to blame for war in Africa. Gem diamonds are a luxury item and ironically, the industry has been working for years to promote these diamonds as a symbol for love. Only 20-25% of all mined diamonds go into gemstones and jewelry though; whereas, 75-80% of all diamonds are of great economic importance for industrial applications. One has to wonder if this smear campaign against the diamond industry originated for political, social, or economic motivations.

    Progress is being made to identify conflict free diamonds. The World Diamond Council has drafted a guide to implementing the Kimberley Process Certification Scheme. This system of warrenties is designed to help the industry avoid conflict diamonds and was adopted by fifty-two governments in November, 2002. Read more about conflict diamonds through a photojournalist's eyes, A Diamond's Journey, www.msnbc.msn.com/id/15842546/0 and from diamondfacts.org, a website sanctioned by the World Diamond Council website.

    For more information visit


    Evaluation

    17. The 4 Cs are cut, clarity, carat weight, and color, and are used to assign a financial value to diamond. To obtain a diamond within a certain price range, the four criteria will need to vary. Cut is the most important factor and should never be compromised, therefore a smaller carat weight might be necessary to stay within your price range, if all other factors are also kept high.

    Fact or Fiction!?! This is a fact.

    For more information visit


    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    Diamond image
    taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    18. Moissanite is a type of diamond that has been enhanced.

    Fact or Fiction!?! This is fiction! Moissanite is a synthetic that imitates diamond. Diamond imitations abound and an inexpensive alternative to diamond is found in the interesting use of doubly terminated, clear quartz crystals. One such crystal, dubbed the Herkimer Diamond for its location of origin, Herkimer, New York, can be seen made into jewelry at www.wehug.com/birthstone-April-diamond.html. Diane & Michael McKnight, owners of The Crystal Ball, offers it as an alternative to buying diamond as the April birthstone.

    For more information, visit the diamond-guide.com jewelry store on


    19. According to the Federal Trade Commission, fracture-filled diamond enhancement need not be disclosed to the public.

    Fact or Fiction!?! This is fiction! The FTC stated fracture-filling must be disclosed. In January 2001, the FTC ruled that laser drilling of diamond must also be disclosed.

    For more information, visit The Scheiner Diamonds on


    20. The signs of a good cut are evident by simply looking at the diamond in a face up position.

    This is a fact! If you can use a 10X loupe and here are a few pointers for you to look for...

    • Is the sparkle and dispersion uniform across the whole stone?
    • Is the table (octagon shape) centered and symmetrical, with edges meeting at sharp points?
    • Looking straight down through the table, is the culet (point at the bottom of the stone) small to very small, centered, and a flat polished surface (not broken or chipped)?
    • Find the square (formed by projecting the edges of the octagon on out to the points of the star facets which project out from the table). Are the sides of the square straight, slightly bent in, or bend out? The proportions of the diameter of the table to the entire width of the stone, can be estimated using the lines defining the square. Diamonds should have a table range from 53-64%; smaller tables have more fire (rainbow of color), while larger tables, more brilliance (white light). When the sides of the square are slightly bent in, the table is around 53-58%. When the sides are straight, the table is around 59-62%. If the lines bow out slightly, the percent may be 64% or higher, and the table will seem to spread across most of the crown surface. A wide table is usually a good indication that the overall cut or proportions are not ideal.

    Image taken from
    a former site at
    adiamondisforever.com,
    sponsored by The
    Diamond Trading Company

    1 B.C.E. is "before the common era," also referred to as B.C.

    The material for this section came primarily from:

    Return to the Syllabus or go on to the next lecture.

    This page originates from the Earth Science department for the use and benefit of students enrolled at Emporia State University. For more information contact the course instructor, S. W. Aber, e-mail: saber@emporia.edu Thanks for visiting! Webpage created: 1999; last update: 21 January 2014.

    Copyright 1999-2014 Susan Ward Aber. All rights reserved.