Geology and Mineralogy of Gemstones. David Turner R.
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gem washing in Madagascar. Photo by V. Pardie...Figure 6.29 Examples of exceptional corundum gemstones. Left: In the collect...Figure B6.1.1 Geology of the Island of Naxos (Urai & Feenstra, 2001 ...Figure B6.2.1 Geological map showing the location and geological setting of ...Figure B6.2.2 Rudimentary yet effective mine workings pepper the landscape. ...Figure B6.2.3 Ruby (left, ~1.5 cm) and spinel (right) hosted in soft marble ...
7 Chapter 7Figure 7.1 The faceted and carved Dom Predo Aquamarine (10,363 carats, from ...Figure 7.2 Crystal structure of beryl looking just off the c axis, along the...Figure 7.3 Crystal structure of beryl looking perpendicular to the c axis; n...Figure 7.4 Diagram of substitutions for aluminum by various cations, shown a...Figure 7.5 These phenomenal 15,256 carat unheated rough and 1,000 carat face...Figure 7.6 These red beryl crystals on altered rhyolite matrix are from the ...Figure 7.7 This cluster of aquamarine crystals are from Pakistan and exhibit...Figure 7.8 This morganite crystal from Pala (California) shows a common form...Figure 7.9 These heliodor crystals on matrix (host rock) show excellent tran...Figure 7.10 This dark blue beryl crystal shows good clarity in the deeper to...Figure 7.11 This faceted dark blue beryl crystal is the same crystal as that...Figure 7.12 This piece of rough euhedral emerald originates from the Ghost L...Figure 7.13 Gem‐quality euhedral emerald crystal hosted in calcite from Cosc...Figure B7.1.1 Left: Relative strengths of light absorbance (light being lost...Figure 7.14 These cut beryl specimens range in weight from 911 to 2,054 cara...Figure 7.15 The “Chalk Emerald” from Colombia is large at 37.8 carat and is ...Figure B7.2.1 The Mogul Emerald. Keller (1981) / with permission of Gemologi...Figure B7.2.2 The Hooker Emerald. Smithsonian National Museum of Natural His...Figure 7.16 Open pit mining at the Kagem Emerald Mine in Zambia. Photo from ...Figure 7.17 Cross‐section and internal structure of a complex pegmatite, not...Figure 7.18 An hypothetical magma and some of the mechanisms by which beryl ...Figure 7.19 The interaction of hot magmatically‐derived hydrothermal fluids ...Figure 7.20 Green emerald crystals hosted in white quartz vein from the Tsa ...Figure 7.21 Schematic formation model of red beryl at the Ruby Violet Mine, ...Figure 7.22 This specimen of red beryl was fractured at some point in its ge...Figure 7.23 Geographic distribution of main emerald deposits (green circles ...Figure 7.24 This emerald specimen, still in its host rock, is also from Colo...Figure 7.25 Local geological setting (a) of emerald deposits from the Wester...Figure 7.26 These emeralds (~5–23 carats) from Penas Blancas mine in Colombi...Figure 7.27 Geological cross‐section (left) at Habachtal, Austria, and simpl...
8 Chapter 8Figure 8.1 Three photos showing ranges of scale for pegmatites, from small (...Figure 8.2 Schematic representation of regional geochemical zoning in pegmat...Figure 8.3 Trace element composition of potassium feldspar from the Luumaki ...Figure 8.4 Schematic drawings of simple to complex pegmatites. (a) is a simp...Figure 8.5 Mapped vertical cross‐section of a tourmaline‐bearing pocket from...Figure 8.6 Cross‐section and zoning patterns seen in a complex pegmatite dyk...Figure 8.7 Geological map (left, a) and cross‐section (left, b) of the Luuma...Figure 8.8 Partially corroded beryl (var. aquamarine) crystal. Corbin17 / Al...Figure B8.1.1 Oxygen isotope values in corundum showing that certain types o...Figure B8.1.2 Boron isotope compositions in a variety of geological settings...Figure B8.1.3 Trace element compositions of bismuth, lead, and gallium for c...Figure B8.1.4 Laser induced breakdown spectroscopy (LIBS) is being increasin...Figure 8.9 These crystals of black schorl are hosted in quartz veins cutting...Figure 8.10 Slice of watermelon tourmaline with euhedral shape alongside the...Figure 8.11 Elbaite tourmaline (var. indicolite) on quartz matrix from Minas...Figure 8.12 Crystal structure of tourmaline looking just off the c axis (lef...Figure 8.13 Part of the tourmaline mineral species classification scheme bas...Figure 8.14 Examples of color in the tourmaline group of minerals, although ...Figure 8.15 Two examples of the mineral elbaite but showing different colors...Figure 8.16 Canary yellow tourmaline (fluor‐elbaite) from eastern Zambia, 50...Figure 8.17 Green tourmaline set with platinum and diamonds. Photo by D. Tur...Figure 8.18 Rubellite variety of gem tourmaline with heavy purple overtone. ...Figure 8.19 Color‐zoned elbaite from Antananarivo, Madagascar (left) and an ...Figure 8.20 Three examples (top) of Paraíba‐type tourmaline from Brazil, Nig...Figure 8.21 These two plots show the absorption spectra in the visible‐to‐ne...Figure 8.22 Faceted and rough prismatic spodumene crystal. Note the roughly ...Figure 8.23 Crystal structure of spodumene, a lithium‐ and aluminum‐bearing ...Figure 8.24 Photograph of the Etta Mine in South Dakota circa 1904 (top) fro...Figure 8.25 Kunzite weighing 104.66 carats from Brazil. Photo from Royal Ont...Figure 8.26 Left: spodumene in unpolarized “normal” light, as your eye would...Figure 8.27 Green hiddenite specimen from North Carolina, USA (left), is 4.6...Figure 8.28 Crystal structure of topaz looking slightly oblique down the c a...Figure 8.29 The faceted stone “American Golden Topaz” (left), 22,892.5 carat...Figure 8.30 Natural blue topaz, ~4 cm tall, on albite and micas from Mursink...Figure 8.31 Simplified geological map of the Klein Spitzkoppe topaz‐bearing ...Figure 8.32 Schematic of topaz‐bearing rhyolite dome and flows. Note the occ...Figure 8.33 Euhedral topaz crystals (~2 cm) formed in lythophysae (gas cavit...Figure 8.34 Microphotograph of euhedral topaz crystals in quartz‐calcite vei...Figure 8.35 Cognac‐colored Imperial topaz (left), 875.4 carats rough, 94 car...Figure 8.36 Gold ring with pink topaz and diamonds. Locality unknown.
9 Chapter 9Figure 9.1 The crystal structure of chrysoberyl, showing BeO4 tetrahedra in ...Figure 9.2 Cat’s eye chrysoberyl from gem placers in New South Wales, Austra...Figure 9.3 This chrysoberyl gemstone is from Minas Gerais (~115 carats) and ...Figure 9.4 The Whitney Alexandrite from Minas Gerais – possibly one of the f...Figure 9.5 Deposit model schematic for the pegmatite‐related Franqueira (Spa...Figure 9.6 Regional geological map (upper left, A) and geologic vertical cro...
10 Chapter 10Figure 10.1 The Imperial State Crown of the United Kingdom prominently displ...Figure 10.2 The crystal structure of spinel, with MgO4 tetrahedra in orange ...Figure 10.3 A collection of spinel of various colors from the Luc Yen area, ...Figure 10.4 Blue spinel colored by cobalt from Baffin Island (Nunavut, Canad...Figure 10.5 Faceted and rough spinel from Mogok (Myanmar, formerly Burma), w...Figure 10.6 Marble‐hosted red spinel from the Luc Yen area, Vietnam. Van Lon...Figure 10.7 Scanning electron microscope images of a spinel crystal hosted i...Figure 10.8 Geological map of the Luc Yen area (Vietnam) with primary in sit...Figure 10.9 Schematic of spinel (blue) formation in marbles of the Luc Yen a...Figure 10.10 Oxygen isotope values for purple, pink, red, blue, and orangy s...
11 Chapter 11Figure 11.1 Crystal structure of zoisite (parent mineral of tanzanite), with...Figure 11.2 Tanzanite with fantastic deep violet‐blue color and weighing 122...Figure 11.3 Tanzanite before (left) and after (right) heat treatment, with g...Figure 11.4 Location of the tanzanite deposits in the Merelani Hills. Olivie...Figure 11.5 Schematic 3D diagram of tsavorite mineralization environments wi...Figure 11.6 The four mining blocks that host tanzanite mineralization. Block...
12 Chapter 12Figure 12.1 Left: rough (43.30 carats) and cut (13.88 carats) pink pyrope, l...Figure 12.2 Crystal structure of spessartine, Mn3Al2(SiO4)3, looking down th...Figure 12.3 Left: fire‐red Bohemian chromium‐bearing pyrope garnet (Schlüter...Figure 12.4 Geological schematic for the formation and subsequent transport ...Figure 12.5 Ternary plots of garnet compositions and probable provenance fro...Figure 12.6 Green demantoid (andradite) garnets set with diamonds and white ...Figure 12.7 Green demantoid (chromium‐bearing andradite) garnets from the Ur...Figure 12.8 Genetic models for tsavorite garnet nodule formation in the Moza...Figure 12.9 Fine lamellae in iridescent garnet from Nara Prefecture, Japan (...Figure 12.10 Pink (incandescent) to purple (LED) color‐change pyrope garnet....Figure 12.11 Color‐change characteristics of a selection of vanadium‐bearing...
13 Chapter 13Figure 13.1 The crystal structures of jadeite (left, a pyroxene group minera...Figure 13.2 White nephrite jade disc (~5.5 cm across) from Qing Dynasty. Its...Figure 13.3 This piece of carved jade weighs 13 carats and is of top quality...Figure 13.4 Blue jadeitite from the Motagua River area of Guatemala, often r...Figure 13.5 Generalized formation model for jadeitite deposits from Harlow e...Figure 13.6 Cross‐section (and thin section sketch) through a jadeitite vein...Figure 13.7 Global distribution of jadeitite deposits with the trace of plat...Figure 13.8 Schematic of altered argillite with rind of seminephrite and act...Figure 13.9 Schematic of nephrite associated with dolomitic marble at the Ch...Figure 13.10 A map of the distribution of jade throughout