Re: Photo Atlas Of Inclusions In Gemstones Pdf Free Download
Anna Pybus
The first volume of the Photoatlas of Inclusions in Gemstones is a landmark work that established the importance of inclusions as an aid to identifying gemstones and deepens our understanding of gems and their origins. This volume covers known microscopic characteristics of gem materials up to 1986. It includes over 1400 color photomicrographs that illustrate common features in gemstones from particular localities as well as various types of inclusions that help separate natural from synthetic gemstones. Eduard J. Gubelin & John I. Koivula, Hardcover, 4th (2004), 532pp
One of the most important features of Photoatlas Volume 3 is the extensive coverage of synthetic and treated varieties of the major gems. This is invaluable for working gemologists and jewelers and makes Volume 3 truly a standout. Want to know the inclusions of Ramaura synthetic ruby? There are pages of examples (including some real stunners). How about treated diamonds or sapphires? Also present. From filled emeralds through beryllium-treated rubies and sapphires, the enhancement oyster is here in toto. Even the various forms of natural and man-made glass are well represented. I was also delighted to see each major section start with an essay and a solid bibliography. This is a welcome change from previous volumes, which tended to be light on references.
John Koivula has had a passion for the science of inclusions in gems and minerals since childhood. For him, a serious avocation led to a formal education in chemistry and geology, and subsequently, a career in gemology. His keen interest in the microworld of gemstones has produced seminal gemological research and the development of many new and useful techniques for photomicrography of gemstones.
Photoatlas Volume 3, the final volume in the highly praised series, Photoatlas of Inclusions in Gemstones, focuses on inclusions in the major commercial gems (diamonds, rubies, sapphires, and emeralds) and inclusions in rare and unusual host materials, such as ekanite and taaffeite.
This last book in the Photoatlas library concludes the 35-year collaboration of the renowned gemological authorities, E. J Gübelin and J. I Koivula. With the completion of Volume 3, Gübelin and Koivula have provided gemologists with the complete, authoritative photomicrographic reference volumes on inclusions in gemstones.
Flux fingerprints can resemble natural finger prints, the flux can look white,yellow or orange; upon close examination a gemologist would notice that the flux inclusions are opaque compared to natural liquid filled fingerprints. (Gübelin and Koivula Photoatlas Vol.3)
Figure 4-4.2 are images in darkfield of a 1.99 ct synthetic Chatham flux grown ruby crystal. The flux inclusions resemble fingerprints, yet notice the undulating structure, and undissolved flux residue in the channels; this is proof of synthetic origin (Emmett 2005) (Gübelin and Koivula photo atlas vol. 3)
Small intact prismatic inclusions and natural finger prints, along with two phase incisions indicate natural origin. Looking at as many pre-identified gemstones as possible is the key in fully understanding what is being observed.
John Koivula, the famous photomicrographer behind the Photoatlas series, has graciously donated some of his images to the database.
If others would like to contribute, we would take that into consideration. However, I know many photographers are wary of putting their work up online because they are concerned about images being used without proper credit, which is a legitimate concern.
The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are its mass in carats (a carat being equal to 0.2 grams), cut (quality of the cut is graded according to proportions, symmetry and polish), color (how close to white or colorless; for fancy diamonds how intense is its hue), and clarity (how free is it from inclusions). A large, flawless diamond is known as a paragon.[88]
Part of the reason that gemstones reach such high values is their rarity. A typical diamond deposit yields 5 grams of gems per million grams of mined material, with only 20 percent of the gems being of jewelry quality. Like oil, gems can take an immense stretch of geologic time to form. Radioactive-decay dating of microscopic inclusions in diamonds has found these gems to be 970 million to 3.2 billion years old. Thus high-quality gems can be mined out much faster than they are produced, essentially making them a finite resource. For instance, one emerald mine established in 1981 in Santa Terezinha, Brazil, produced a peak of 25 tons of rough stones valued at $9 million in 1988; the same tonnage of stones mined in 2000 sold for only $898,000. This scarcity also makes gemstones highly valuable to geologists. Exceptional geological conditions are required to produce gem deposits. The desire to unravel the history of such unusual circumstances is drawing increasing numbers of Earth scientists to the study of gems and their origins.
Some years ago I was also introduced to a much more specialized microscopy method by my good friend and microscopy mentor John Koivula, who is a highly accomplished photomicrographer and microscopist. That method is episcopic differential interference contrast, or Epi-DIC, which has much more limited application, but is useful for carefully examining the surfaces of gemstones which can be used to detect treatments in some cases. Aside from the practical uses for Epi-DIC, I really enjoy the aesthetics of the bright colors and geometric forms I see on the surfaces of etched gem minerals that this microscopy technique provides.
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