Silver – Coconino Lapidary Club

Native Silver – Part I

Mineral Man Mel — Sun, 13 Oct 2024 00:12:47 +0000

This is the first of two Blogs on native silver. In the first I will introduce the mineral, including a gallery of specimens, and in the following blog, “Ancient Silver Jewelry” I’ll present examples of ancient silver jewelry, coinage, and art works, which demonstrate the innovative artisanship of early silversmiths from varied locations around the world.

Among the native elements, silver, [Ref 1], is a favorite among mineral collectors, as it is for me. Silver offers variations in color from metallic silver-white to the optical interference colors of a thin coating film, (such as on copper sulfide minerals – see my earlier Copper Blog), to the sooty black of a thick coating. From locations around the world it occurs in a number of aesthetic and geometrically interesting forms, ranging from groupings of single crystals (Figures 1-2), spectacular fern-like dendritic arrays of crystals (Figures 3 & 4), and striking wire and sheet forms (Figure 5 & 6). The relative arrangement of crystals in, and the shape of, the dendrites has been found to depend on the conditions of the surrounding silver-bearing solution during deposition of the silver, [Ref 2]. Specimens of wires attached to the silver sulfide acanthite, (Ag₂S), grow on oxidation of the sulfide mineral, which liberates the silver, as described below, both by roasting, [Ref 3], or by chemical reactions in solutions within both the oxidized and replacement zones of an ore body, (Slide 9 of [Ref 4]). The wires grow at the interface between the acanthite and silver by continuing the face centered cubic lattice shared by both the acanthite and the silver, [Ref 1]. The sulfur of the acanthite occupies the interstices between the silver atoms. X-Ray diffraction and microscopy have demonstrated the crystallinity of a native silver wire.

In order to share with you these beautiful and intriguing forms of native silver, I’ve included a comprehensive gallery of these forms from around the world, (Figures 3-17). I’ve also taken the liberty of including a favorite specimen from my silver collection in the gallery, (Figure 10).

Because the lore of lost precious metal mines, particularly those in Arizona, New Mexico, and Nevada fascinate many of us; I’ll begin referencing descriptions and histories of these mines and provide brief excerpts from the references. In this blog, the emphasis will be on lost silver mines and in future blogs on silver minerals. Future blogs on Gold and Gold minerals will also include lore & history of lost Gold mines.

Silver Crystal Forms

Silver belongs to the isometric crystal system, [Ref 1], and crystallizes in cubic and octahedral forms as shown in Figures 1 and 2. The forms reflect the symmetry of the isometric crystal system. Silver crystals form twins on the octahedral surfaces of two crystals resulting in a Spinel-Twin, [Ref 6], with the remainders of each of the octahedrons visible, as seen in Figure 3.

Figure 1. Silver crystal in octahedral form, [Ref 1]

Figure 2. Silver crystal in cubic form, [Ref 1]

Figure 3. Twinned silver octahedrons, a Spinel-Twin, [Ref 1, 7]

GALLERY OF NATIVE SILVER SPECIMENS

Figure 4. Cubic crystals of native silver on calcite, Kongsberg silver mining district, Buskerud, Norway.

Figure 5. Dendritic silver comprising an array of branches twinned on octahedral faces (Spinel twins, [Ref 3]), Batopilas, Andre del Rio District, Mun. de Batopilas, Chihuahua, Mexico.

Figure 6. Dendritic silver in quartz, comprising arrays of silver crystals twinned on octahedral faces (Spinel-Twins), Creede District, Mineral County, Colorado.

Figure 7. Dendritic silver on native arsenic. Pohla Mine Group, Freiberg, Saxony, Germany. The dendrites feature growth of branches from cubic faces to give mutually perpendicular orientation with respect to the central branch, instead of from octahedral faces as in Figure 4.

Figure 8. Dendritic silver in calcite, “The Road Runner” Batopilas, Andre del Rio District, Mun. de Batopilas, Chihuahua, Mexico.

Figure 9. Wire silver growing from acanthite, Reyes mine, Gunaajuato, Mexico. Note the close relationship between the base of the rams-horn-shaped silver wire and its host acanthite crystal.

Figure 10. Wire silver growing from acanthite crystals, Linquiu, Shanxi Province, China. Note the intimate contact between the acanthite crystal and the silver wire.

Figure 11. Wire silver, Himmelsfurst Mine, Brand-Erbisdorf, Freiberg District, Saxony, Germany.

Figure 12. Silver wire with acanthite in calcite, Kongsberg silver mining district, Buskerud, Norway.

Figure 13. Native silver crystals with native copper crystals, White Pine Mine, Ontonagon County, Michigan. An interesting association found at this locality.

Figure 14. Distorted cubic silver crystals on copper. Wolverine Mine, Houghton County, Michigan.

Figure 15. Sheet silver, Morenci Mine, Copper Mountain District, Shannon Mountains, Greenlee County, Arizona. The sheet-like form arises from crystallization of small crystals in a closely confined space.

LOST SILVER MINES

The location of the Lost Duppa Silver Mine in Arizona, [Ref 8], lies in the numerous mines and ore deposits of the heavily mineralized Bradshaw Mountains, (Figures 11-16). When discovered, the deposit was a ledge of silver-bearing quartz located in one of the many steep canyons located on the east side, of the northern Bradshaw Mountains. The ore was native silver. After his initial find, Duppa failed to relocate his original path to the deposit and never found it again.

Figure 16. Bradshaw Mountains as viewed from Cow Creek Road, an access road to the mountains, [Ref 9].

Figure 17. The Tip Top Mine, Bradshaw Mountains, [Ref 10].

The Lost Silver Lode of Carbonate Creek, New Mexico, [Ref 11]

The discovery of lode was in the Kingston Mining District, located in the southern region of the Black Range in Southwestern New Mexico. Located within the range are the Chloride, Kingston, and Hermosa Silver Distracts which have been rich producers of the metal. The lost lode lies in the Kingston Silver Mining District shown in [Ref 12], which eventually produced silver amounting to over Six Million in USD. The lost lode was discovered along Carbonate Creek near the town of Kingston as surface float of acanthite (silver sulfide). The weights of pieces of the float ranged up to 250 pounds. Ultimately float yielding over 80,000 ounces was found, but the source of the float was never discovered.

Silver Part II – A Gallery of Silver Jewelry

Mineral Man Mel — Sun, 13 Oct 2024 00:12:47 +0000

This gallery of beautiful silver jewelry, coinage, and art works presents works from around the world, and spanning the ages from the 26^th Dynasty of Egypt (664-525 BC) to the Art Deco Era (1909-1941 AD) [Ref 1, 2]. Works have been chosen to demonstrate the artisan’s methods of forming shapes in silver [Ref 3] by casting, engraving, repousse’, embossing, and using silver inlay to adorn other metal objects [Ref 4]

[metaslider id=1788]

References

Ref 1. https://en.wikipedia.org/wiki/Twenty-sixth_Dynasty_of_Egypt

Ref 2. https://artdeco.org/what-is-art-deco/early-20th-century-timeline

Ref 3. https://en.wikipedia.org/wiki/Silversmith

Ref 4.https://en.wikipedia.org/wiki/Inlay

Ref 5. http://www.busaccagallery.com/catalog.php?catid=141&itemid=5619

Ref 6. http://www.ancientresource.com/lots/ancient_jewelry/diannesommelet/diannesommelet2.html

Ref 7. https://www.secretenergy.com/illustrations/cultures/mesopotamia/

Ref 8. http://www.getty.edu/art/exhibitions/ancient_luxury/

Ref 9. http://www.historyandcivilization.com/Picture-Gallery—Early-Mesopotamia-from-Sumer-to-Assyria—Artifacts–Objects—Sculpture.html

Ref 10. https://www.pinterest.com/pin/354799276868988412/?lp=true

Ref 11. http://www.antiques.com/classified/1112715/Antique-Huge-Roman-Silver-Ring-w–Portrait#

Ref 12. https://www.ngccoin.com/news/article/6078/ancient-coins/

Ref 13. http://www.britishmuseum.org/research/collection_online/collection_object_details.aspx?assetId=973486001&objectId=154939&partId=1

Ref 14. https://www.archaeology.org/issues/149-1409/artifact/2388-denmark-viking-figurine

Ref 15. https://art.thewalters.org/detail/40080/signet-ring-2/

Ref 16. http://www.getty.edu/art/exhibitions/ancient_luxury/

Ref 17. https://boylerpf.com/products/antique-victorian-silver-italian-coral-bracelet

Ref 18.https://boylerpf.com/products/vintage-italian-silver-carnelian-art-deco-bracelet

USE OF COLOR IN MINERAL IDENTIFICATION

Mineral Man Mel — Thu, 03 Jun 2021 18:48:41 +0000

In some minerals color is directly related to a metallic element, is characteristic, and can be useful in identification. As examples, azurite as shown in Figure 1A, is always blue due to the presence of copper, and rhodochrosite, shown in Figure 1B, is always pink to red due to the presence of manganese,. However minerals such as fluorite, colorless in it self, can be yellow, blue, purple, or green due to low concentrations of metal impurities.

Accordingly color alone, generally is insufficient for identification, but when linked with knowledge of other properties of a mineral can be useful in its identification.

Understanding of the roles of metals as sources of colors in a mineral, particularly when augmented with knowledge of its location where found, can be useful in identification. In this Blog I’ll describe how the presence of a transition metal element, present intrinsically or as an impurity, and certain structural features within the mineral are sources of colors or when present, can modify the appearance of the mineral.

Figure 1A. Azurite, Czar Mine, Copper Queen Mine, Queen Hill, Bisbee. Cochise County, Arizona[Ref1]

Figure 1B. Rhodochrosite, N’Chwaning Mines, Kuruman. Kalahari Manganese
Field, Northern Cape, South Africa[Ref2]

CAUSES 0F COLORS AND COLOR EFFECTS IN MINERALS

The color of a mineral that we see arises from transmission of light over the visible wavelengths of light within the visible light spectrum which are framed by one or more regions of wavelengths that are absorbed as shown in Figure 1C.

Figure 1C. With absorption of specific wavelength{s) of white light spanning wavelengths of red to purple results in transmission of light over a wavelength range imparting color[Ref3]

Extensive studies have shown that light absorption by a number of processes are among the causes of the colors in minerals as summarized in TABLE I[Ref4].

Absorption of light by electrons in transition metals present intrinsically or as impurities are involved in light absorption processes and the excitation of electrons within their intrinsic energy distribution within conductors and semiconductors upon light absorption also imparts colors in other minerals which are conductors and semiconductors. Excitation of an electrons or a hole (hole = absence of a negatively charged ion or electron) associated with color centers which reside in defects within the crystal lattice imparts colors in some minerals

Structural features in minerals with sizes of the order of the wavelengths cause physical optical effects: light scattering, interference, and diffraction of light. These can either introduces colors or add optical features to the appearance of the mineral.

TABLE I. CAUSES OF COLORS AND COLOR EFFECTS IN MINERALS[Ref4].

Light Absorption by Transition Metals[Ref4,5,6]

Among the causes of color in minerals listed in TABLE I[Ref4] are the ions of transition metals that contribute to the color of many minerals through selective light absorption over the visible light spectrum. They can be present as a major constituent such as manganese (Mn) in rhodochrosite(MnCO₃) giving it its pink-red color, present as a low concentration impurity in a mineral such as chromium (Cr)substituting for aluminum (Al) in Ruby giving its red color and the formula {Al,Cr_minor)₂O₃, and as ions of iron, chromium , manganese, titanium(Ti) participating in intervalence charge (electron) transfer between two of their ions and with the oxygen ion[Ref5].

Transition metals are present as a formulaic constituent and some as an impurity are shown along with their associated colors in TABLES II and III.

In a transition metal ion with a partially filled d-shell the electrons in the outer region of the d-shell are unpaired. The surrounding oxygen ions of the crystal lattice exert forces on the outer d-shell electrons dermining their occupied and empty energy levels[Ref5]. The forces and energy levels depend on the strength and nature of the bonding as well as the valence of the transition metal ion. These energy levels are quantized so that a absorption of a specific amount energy is required to to increase an electrons energy to another level. Absorption of light of that energy at the corresponding wavelength provides the energy required for excitation of the unpaired electron to a higher level.

As an example consider absorption and transmission of light in the ruby. The sumation of surrounding forces on the chromium ion Cr³⁺ result in two energy levels, C and D, avialable for an excited electron as shown in Figure 2[Ref3]. Symmetry conditions deny occupancy of level B by an excited electron [Ref].

As shown in Figure 3 light of 414 and 561 nm wavelengths is absorbed . With abosrbtion of these wavelengths light in the regions of 480 nm and greater than 620 nm are transmitted imparting the red color of the ruby.

Figure 2. Excitation of d-elecrons in Cr³⁺ in a ruby crystal upon absorption of 414 nm (2.99 eV) ultraviolight light and of 561 nm (2.21 eV) yellow- green light[Ref]. The peak abosorption and transmission of light within the ruby at these wavelengths are shown in the two spectra shown in Figure [Ref3]

Figure 3. Transmittance spectrum (Right) of a 1-cm thick ruby crysta[Ref4]. Absorptioon of light is greatest at 414 nm and 561 nm and transmittance in the blue at 480 nm and in the red at wavelengths greater than 620 nm in the red.

TABLE II. TRANSITION METALS PRESENT AS AN INTRINSIC CONSTITIUENT IN A MINERAL AND ASSOCIATED COLORS[Ref5,6]

TABLE III. TRANSITION METALS PRESENT AS AN IMPURITY IN A MINERAL AND ASSOCIATED COLORS[Ref5,6].

Light Absorption By Charge Transfer Between Transition Metal Ions and Between oxygen ions and Transition Metal Ions[Ref7,8].

Transition metals can exist in different valence states. These ions can form covalent bonds with oxygen in which electrons in outer shells can travel between the ions upon being supplied sufficient energy. This can result in charge transfer in the form of an electron upon absorption of light with wavelengths in the Ultraviolet through Visible into Near Infrared light ranges. Charge transfer from an adjacent oxygen to a transition metal ion and charge transfer between neighboring transition metal ions connected by an oxygen atom can occur. The direction of transfer charge is from the ion of least positive valence number to the neighbor of higher valence. For example the deep violet-blue color of cordierite var. Iolite as shown in Figure 4 results from the neighboring absorption peak centered at 600 nm due to charge transfer from a ferrous ion Fe²⁺ to a neighboring ferric ion Fe³⁺, and extending through the blue range of the spectrum as shown in Figure 5[Ref10]. Other examples of the processes of charge transfer in minerals with their associated colors are given in TABLE IV.

Figure 4. Cordierite var. Iolite, Mogok, Pyin-Oo-Lwin District, Mandalay Region, Myanmar[Ref9].

Figure 5. Absorption spectrum of cordierite var. Iolite from Tamil Nadu, India[Ref10].
Note that the wide absorption peak in the 400 to 600 nm range results in a transmission window in the violet.

TABLE IV. CHARGE TRANSFER PROCESSES IN SOME MINERALS WITH THEIR COLORS

Charge Transfer	Color and Mineral*	Reference
Oxygen to Metal Transfer
O^2-  Fe³⁺	Yellow to Brown: beryl/heliodor, quartz/citrine	11
O^2–  Fe⁴⁺	Purple: quartz/amethyst	11
O^2-  Cr⁶⁺	Yellow to red: Crocoite	11
O^2- U⁶⁺	Yellow: uranophane	11
Intervalence Charge Transfer
Fe²⁺–O—Fe³⁺	Violet: jadeite Blue: lazulite, vivianite,	11,12
Fe²⁺–O—Ti⁴⁺	Blue: berlaquamarine, corundum/sapphire, cordierite, amphibole,	11
Mn²⁺–O—Ti⁴⁺	Greenish-yellow: tourmaline	11
Others
Fe²⁺Ti⁴⁺ and both Fe³⁺ and Cr³⁺	Orange, sapphire	13

*For information on any mineral Google “Mindat.org + Mineral name”

Light Absorption By Color Centers[Ref4]

Unpaired electrons can be located on a non-transition metal ion or on a defect in the crystal lattice form color centers as shown in the Fluorite structure and quartz structure shown in Figures 5 and -6. An electron present at a lattice vacancy forms an electron color center and absence of an electron from where an electron pair is normally present forms a hole (lack of a negatively charged ion) center.

In fluorite the absence of a fluorine ion F^-1 from its normal position forms an F-center occupied by an electron as shown in Figure 6. Absorption at longer wavelengths by the F-center is responsible for a purple color in fluorite[Ref5].

In smoky quartz the presence of an aluminum ion Al³⁺as a low level impurity substituting for a silicon ion Si⁴⁺is required[Ref5]. Removal of an electron from an oxygen ion O^2- adjacent to aluminum ions by radiation results in the formation of a singly negative oxygen forming an electron-hole. To preserve charge neutrality a positive hydrogen ion H+ is present. Aluminum not substituting for silicon does not form smoky quartz. The same mechanism accounts for the yellow color of citrine[Ref11].

Figure 6. Schematic of normal fluorite structure (A) and fluorite with an
F-center occupied with an electron (B)[Ref5].

Figure 7. Schematic of the normal quartz structure (A) and containing impurity aluminum ions Al³⁺ replacing silica ions Si⁴⁺in the lattice (B)[Ref5]. Radiation has removed an electron from oxygen leaving a hole center of smoky quartz. To preserve charge neutrality a positive hydrogen ion H+ is present. Aluminum not substituting for silicon does not form smoky Quartz.

Light Absorption in Metals and Semiconductors: Band Theory[Ref5]

The band theory treats electrons as belonging to the crystal as a whole and capable of occupying bands or ranges of energies as shown for metals and semiconductors in Figures 8 and 9.[Ref5]. Colors of representative minerals described by band theory are shown in TABLE IV.

TABLE IV. COLORS OF METALS AND SEMICONDUCTORS DESCRIBED BY BAND THEORY[Ref5].

The Band Theory of Metals[Ref5]

In a metal such as copper or iron each metal atom contributes its outer electrons to a common pool in which they are free to move freely through the crystal accounting for the large electrical conductivity of metals as well as the metallic luster and specular reflection of metals. In a typical metal which contains 10²³ electrons per cm^-3 all essentially equivalent to each other, such that quantum mechanically

the energy levels are broadened into bands as shown in Figure 8A. The density of electrons each energy level is limited and states are filled to the maximum Fermi surface (level). Upon absorption of light electrons are excited to empty bands of higher energy with density of states varying with as shown in Figure 8B.

If the efficiency of absorption decreases with increasing energy in the blue-green spectrum as in gold and copper the spectrum features the yellow and reddish colors of gold and copper upon reemission of the electrons as shown by the reflectance spectra shown in Figure 9[Ref18]. The spectra of silver and aluminum in the figure show that light across the visible spectrum is absorbed and re-emitted leading to their white color.

Figure 8. Energy band of a typical metal (A) and showing energy transitions upon light absorption (B)[Ref5]. The Fermi Surface is the maximum energy of an electron in the valence band.

Figure 9. Reflectance (or fraction of light reflected) spectra of aluminum (Al), Silver (Ag), gold(Au), and copper(Cu)[Ref14] as also shown in the specimens in Figures 10-12.

Figure 10. Native silver on native arsenic, Pohla-Tellerhauser mine, Pohla, Saxony, Germany[Ref15].

Figure 11. Group of twinned native gold crystals, Round Mountain Mine, Round Mountain, Round Mountain Mining District, Toquima Range, Nye County, Nevada[Ref16].

Figure 12. Twinned crystals of native copper, Chino Mine, Santa Rita, Santa Rita mining district, Grant County, New Mexico[Ref17].

Figure 13. Energy bands in a typical semiconductor (A), energy transitions upon light absorption in (B), the dependence of color on energy(C), and the color stemming from a band gap of that energy (D)[Ref5].

The Band Theory of Semiconductors[Ref5]

Many sulfide minerals are semiconductors that exhibit substantial electrical conductivity, high refractive indices, and often a metallic luster[Ref4]. In minerals where bonding is predominantly covalent or ionic the sulfur electrons occupy a valence band as shown in Figures 13A and 13B. A band comprised of empty metal electron orbitals exists at higher energies separated from the valence band by an energy gap as shown in Figure 13. Absorption of light by electrons of energy greater that the gap energy excites them into the conduction band as shown in the Figures 13C and 13-D. If the band gap is smaller that the energy of the visible light range all of the light is absorbed and the mineral behaves like a metal and appears black or grey as shown in Figures 13–C and13 -D and by tetrahedrite with a band gap of 0.000 eV[Ref21] and galena with a band gap of 0.993 eV[Ref 22] and shown in Figures 14 and 15. As the band gap energy increases the wavelengths excited in the spectrum become shorter and colors shift through red to yellow. The band gaps of those semiconductors such as diamond and sphalerite with band gaps of about 5.5 and 3.5 eV are greater than available energy at the lowest wavelength (highest energy) of the visible spectrum and the light is absorbed. With an intermediate band gaps of 1.99 eV and 2.197eV, respectively cinnabar appears red and orpiment yellow-orange as shown in Figures 16 and 17[Ref23].

Figure 14. Hopper crystal of tetrahedrite, Romania[Ref26]. The crystal is black because with a band gap of 0.000 eV tetrahedrite absorbs all visible wavelengths[Ref18,19].

Figure 15. Galena, Sweetwater mine, Ellington, Reynolds County, Missouri[Ref20].

Figure 16. Cinnabar, Almade’n mine, Almade’n, Almade’n Mining District, Ciudad Real, Castle-La Manch, spin[Ref21].

Figure 17. Orpiment, Twin Creeks Mine, Potosi Mining District, Osgood Mountains,
Humboldt County, Nevada[Ref22].

Light Absorption and Colors in Impurity and Defect Semiconductors[Ref5]

Certain impurities can cause light absorption in large band gap minerals. Absorption of light nitrogen and boron impurity centers as shown in Figure A and –B results, respectively in yellow and blue colored diamonds.

Yellow Diamonds

Figure 18. Light absorption in the blue-violet spectral range by a
nitrogen impurity results in the yellow color of a diamond[Ref23].

Figure 19. Yellow diamond of 32.77 carats[Ref27].

Blue Diamond

Figure 20. The boron acceptor atom accepts electrons with energies corresponding to the green to red region of the visible spectrum resulting in transmission of the blue color[Ref23].

Figure 21. The blue Hope diamond[Ref28].

Green Diamond

A green color in a diamond arises from absorption of light in the yellow to red wavelength region by electrons associated with defects in the periodicity of the diamond crystal lattice as shown in Figure [Ref24].

Figure 22. The defects in the diamond lattice that are responsible for a green color in a diamond: In Figure 2.A, absorption by unbonded electrons surrounding a lattice vacancy (missing carbon atom); in 2.B light absorption by unbound electrons surrounding a lattice vacancty associated by a pair of neighboring nitrogen atom impurities; in 2.C light absorption by electrons associated with a hydrogen atom with a neighboring nitrogen atom impurity; in 2.D absorption of light by a defect comprised of two neighboring carbon lattice vacancies with an associated nickel atom[Ref24].

Pink Diamond

Color defect centers developed along deformation planes in the diamond crystal lattice diamond are responsible for the coloration in pink diamonds as shown in Figure23[Ref25,26].

Figure 23. Pink Diamonds, Argyle Mine, East Kimberly region, Australia[Ref39].

Colors and Features Caused by Physical Optics

Play of color due to structural characteristics of the gemstone can be useful in mineral identification. Iridescence, opalescence and labradorescence, chatoyancy, and asterism are characteristics of a limited number of minerals.

Opalescence

Opalescence is an opal-like play of light producing flashes of different colors as in an opal as shown in Figure 24[Ref40]. The various colors are produced by diffraction from regions with layers of different thickness of formed by silica spheres of different uniform diameters[Ref41]

Figure 24. Structure of precious opal showing uniform layers of silica spheres[Ref30].

Figure 25. The “Virgin Rainbow” opal, Coober Pedy, Australia[Ref31]

Labradorescence

Labradorite is a feldspar mineral comprised having striations of exsolved lamellae of nanometer of albite in the 10s to 100sof nanometers size range in anorthite with both having different calcium and sodium concentrations. Accordingly their refractive indices are unequal[Ref39,40] and the striations diffract light giving the colors according to the thicknesses of the lamellae giving the labradorescence as shown in Figure 25[Ref44].

Figure 26. Labradorite cabochon showing striations with alternating lamellae of albite and anorthite of different thicknesses, hence different colors[Ref32].

Iridescence

Iridescence is the play of colors produced in a thin film of different refractive index than in the surroundings and varying thickness such as the wall of a soap bubble or layer of oil on water[Ref45]. Like diffraction the colors depend on thickness and angle at which viewed. The iridescence of some specimens of the copper mineral chalcopyrite as shown in Figure is a classic example of iridescence on a mineral surface where the colors range from blue to red with increasing thicknesses of the film.

Figure 27. Iridescent chalcopyrite, Greystone Quarry, Lezant, Cornwall,
England[Ref34].

Chatoyancy

Chatoyancy is an effect of preferential light scattering by parallel aligned rod like mineral inclusions like the fibers of crocidolite (asbestos) cemented in quartz of the gemstone tigers eye as shown in Figure 28[Ref35,36]. Aligned needle-like microcrystals crystals of rutile are responsible for the chatoyancy of chrysoberyl as shown in Figure .[Ref37]

Figure 28. Chatoyant tigers eye showing aligned structure of crocidolite[Re38].

REFERENCES

Ref 1. https://www.mindat.org/photo-257370.html

Ref 2. https://www.mindat.org/photo-83179.html

Ref 3. http://gemologyproject.com/wiki/index.php?title=Causes_of_color

Ref 4. . https://en.wikipedia.org/wiki/File:Ruby_transmittance.svg

Ref 5. http://www.minsocam.org/msa/collectors_corner/arc/color.htm

Ref 6 https://en.wikipedia.org/wiki/Transition_metal

Ref 7. https://www.higp.hawaii.edu/~gillis/GG671b/Week02/Readings/Deep%20Reading/Burns_CrystalFieldTheory_Ch2and3.pdf

Ref 8. https://www.gia.edu/doc/SP88A1.pdf

Ref 9. https://www.mindat.org/photo-650677.html

Ref 10. http://minerals.gps.caltech.edu/files/Visible/cordierite/Cordierite2016_India.gif

Ref 11. https://www.gia.edu/doc/SP88A1.pdf

Ref 12. http://minerals.gps.caltech.edu/color_causes/ivct/index.htm

Ref 13. file:///Users/millardjudy/Downloads/[20834799%20-%20Advances%20in%20Materials%20Science]%20Heat%20treatment%20enhancement%20of%20natural%20orange-red%20sapphires.pdf

Ref 14. https://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Optical_Properties/Metallic_Reflection

Ref 15. https://www.mindat.org/photo-109627.html

Ref 16. https://www.mindat.org/photo-112379.html

Ref 17. https://www.mindat.org/photo-78563.html

Ref 19. https://materialsproject.org/materials/mp-647164/

Ref 20. https://materialsproject.org/materials/mp-21276/

Ref 21. https://i.pinimg.com/originals/72/26/67/7226674458e6dd34ba15b72f4034130f.jpg

Ref 22. https://en.wikipedia.org/wiki/Hopper_crystal

Ref 23. https://materialsproject.org/materials/mp-641/

Ref 24. https://www.mindat.org/photo-85601.html

Ref 25. https://www.mindat.org/photo-83818.html

Ref 26 https://www.mindat.org/photo-56538.html

Ref 27. http://www.webexhibits.org/causesofcolor/11A0.html

Ref 28. https://www.gia.edu/gems-gemology/spring-2018-natural-color-green-diamonds-beautiful-conundrum

Ref 29. https://www.gia.edu/doc/Characterization-and-Grading-of-Natural-Color-Pink-Diamonds.pdf

Ref 30. https://br.pinterest.com/pin/27092035231593578/

Ref 31. https://www.smithsonianmag.com/travel/the-hope-diamond-102556385/

Ref 32. https://www.pinterest.com/pin/AaGzMFSFFrs9vFLxcvJNl4g6FGLK1W2_i5FGc6i82BuZSmK7fjG7pJ0

Ref 33. http://www.uniqueopals.ch/opal-play-of-colour.htm

Ref 34. http://www.uniqueopals.ch/opal-play-of-colour.htm

Ref 35. https://www.geologyin.com/2016/07/worlds-most-expensive-opal-literally.html

Ref 36. https://www.mindat.org/min-2308.html

Ref 37. https://www.britannica.com/science/exsolution

Ref 38. https://www.google.com/search?client=firefox-b-1-d&q=refractive+index+of+albite

Ref 39. https://www.google.com/search?client=firefox-b-1-d&q=refractive+index+of+anorthite

Ref 40. https://www.sciencedirect.com/topics/medicine-and-dentistry/diffraction-grating

Ref 41. https://austinbeadgallery.com/what-to-look-for-in-labradorite-cabochons/

Ref 42.

https://www.asu.edu/courses/phs208/patternsbb/PiN/rdg/interfere/interfere.shtml

Ref 43. https://www.crystalclassics.co.uk/product/chalcopyrite-(irridescent)/

Ref 44. https://en.wikipedia.org/wiki/Chatoyancy

Ref 45. https://www.asbestos.com/blog/2020/04/20/asbestos-jewelry-mesothelioma/

Ref 46. https://blogs.scientificamerican.com/rosetta-stones/tiger-s-eye-a-deceptive-delight/

Ref 47. https://en.wikipedia.org/wiki/Chrysoberyl#Cymophane

Gold III – Lost Gold Mines in the Southwest

Mineral Man Mel — Fri, 07 Dec 2018 01:37:55 +0000

Tales of the discovery and loss of rich gold mines such as The Lost Dutchman in the Superstition Mountains of Arizona and the El Naranjal lost gold mine in the Sierra Mountains of Mexico, as popularized by folklorist, J. Frank Dobie, in “Apache Gold and Yaqui Silver” have fascinated many of us. An extensive list of both lost gold and silver mines of the Southwest , each with extensive and entertaining descriptions of their histories, can be found in “Lost Treasure Tales” on the GeoZone Site [Ref 1].

Perhaps the lost mine tale that most of us are aware of, is that of the Lost Dutchman Mine [Ref 2]. One, of 62, hand drawn maps of its supposed location, made available in Reference 3, is shown in Figure 1 and orients it with respect to the prominent geological landmark, Weavers Needle, shown in Figure 2.

Figure 1. Map of the location of the Lot Dutchman Gold Mine [Ref 3]

Figure 2. Weavers Needle, the landmark for the location of the Lost Dutchman Gold Mine [Ref 2].

Two roots for the of name of the lost El Naranjal Mine have been attributed to its location near a grove of trees with oranges (naranjas) or to the orange color of the gold in its ore [Ref 3]. It is supposedly located at the bottom of canyon (Barranca) beside a river and near an abandoned hacienda.

Among many of the discussions about this mine, Treasurenet suggests that proof of the its existence lies in an old road sign naming the road to the mine in Sinaloa and in records found in Guadalajara, which were found by a British consul, describing production in the millions in the 17^thCentury [Ref 4]. In another posting,

TreasureNet, [Ref 5], suggests its location fits that of an 1800’s lost, and very rich gold mine, in the region of the lost Tayopa silver mine [Ref 6], and in another post [Ref 7] that its location lies in the state of Durango.

Ref 1. http://www.thegeozone.com/treasure/arizona/index.jsp

Ref 2. http://treasure-hunting-information.com/?page_id=2641

Ref 3. https://en.wikipedia.org/wiki/Naranjal_mine

Ref 4. http://www.treasurenet.com/forums/tayopa/36414-el-naranjal.html

Ref 5. http://www.treasurenet.com/forums/tayopa/273860-can-el-naranjal-possibly-found-tayopa-complex.html

Ref 6. http://www.treasurenet.com/forums/tayopa/36414-el-naranjal.html

Ref 7. http://www.treasurenet.com/forums/treasure-legends/487274-update-mine-el-naranjal.html