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Peridot
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<h2 id="etymology">Etymology</h2> <p>The origin of the name <i>peridot</i> is uncertain. The <i><a href="/facts/Oxford_English_Dictionary/qaxKX8Bc">Oxford English Dictionary</a></i> suggests an alteration of <a href="/facts/English_language/tpkxGt7b">Anglo</a>–<a href="/facts/Norman_language/13RATD7c">Norman</a> <i>pedoretés</i> (classical <a href="/facts/Latin/pM3Kge85">Latin</a> <i>pæderot</i>-), a kind of <a href="/facts/Opal/LF7Xa7nK">opal</a>, rather than the <a href="/facts/Arabic/A1e66hVV">Arabic</a> word <i>faridat</i>, meaning "<a href="/facts/Gemstone/kHffmvE3">gemstone</a>". </p><p>The <i><a href="/facts/Middle_English_Dictionary/XPHBEPcG">Middle English Dictionary</a></i>'s entry on <i>peridot</i> includes several variations: <i>peridod</i>, <i>peritot</i>, <i>pelidod</i> and <i>pilidod</i> — other variants substitute <i>y</i> for letter <i>i</i> used here.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>The earliest use of the word in <a href="/facts/English_language/tpkxGt7b">English</a> is possibly in the 1705 register of the <a href="/facts/St_Albans_Cathedral/S6gqKzQy">St. Albans Abbey</a>: The dual entry is in Latin with the translation to English listed as <i>peridot</i>. It records that on his death in 1245, Bishop John bequeathed various items, including peridot gems, to the Abbey.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="appearance">Appearance</h2> <p>Peridot is one of the few gemstones that occur in only one color: an <a href="/facts/Olive-green/IMkcdPWd">olive-green</a>. The intensity and tint of the green, however, depends on the percentage of <a href="/facts/Iron/QK1JYy8E">iron</a> in the crystal structure, so the color of individual peridot gems can vary from yellow, to olive, to brownish-green. In rare cases, peridot may have a medium-dark toned, pure green with no secondary yellow hue or brown mask. Lighter-colored gems are due to lower <a href="/facts/Iron/QK1JYy8E">iron</a> concentrations.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="mineral-properties">Mineral properties</h2> <h3>Crystal structure</h3> <p>The molecular structure of peridot consists of isomorphic olivine, silicate, magnesium and iron in an <a href="/facts/Orthorhombic_crystal_system/3zo4F8P0">orthorhombic crystal system</a>. In an alternative view, the atomic structure can be described as a hexagonal, close-packed array of oxygen <a href="/facts/Ion/3bePpDna">ions</a> with half of the octahedral sites occupied by magnesium or iron ions and one-eighth of the tetrahedral sites occupied by silicon ions. </p> <h3>Surface property</h3> <p>Oxidation of peridot does not occur at natural surface temperature and pressure but begins to occur slowly at 600 °C (870 K) with rates increasing with temperature.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> The oxidation of the olivine occurs by an initial breakdown of the <a href="/facts/Fayalite/UaPIeQRs">fayalite</a> component, and subsequent reaction with the forsterite component, to give <a href="/facts/Magnetite/SVxoGUs2">magnetite</a> and <a href="/facts/Orthopyroxene/hWMTLF9o">orthopyroxene</a>. </p> <h2 id="occurrence">Occurrence</h2> <h3>Geologically</h3> <p><a href="/facts/Olivine/tLLL4rae">Olivine</a>, of which peridot is a type, is a common mineral in <a href="/facts/Mafic/mVL7Ahuw">mafic</a> and <a href="/facts/Ultramafic_rock/7qAapP1d">ultramafic rocks</a>, often found in <a href="/facts/Lava/q2an5SVN">lava</a> and in <a href="/facts/Peridotite/4NRPpWxw">peridotite</a> <a href="/facts/Xenolith/nP1MlHvG">xenoliths</a> of the <a href="/facts/Mantle_(geology)/RpDdtjCr">mantle</a>, which lava carries to the surface; however, gem-quality peridot occurs in only a fraction of these settings. Peridots can also be found in meteorites. </p><p>Peridots can be differentiated by size and composition. A peridot formed as a result of volcanic activity tends to contain higher concentrations of lithium, nickel and zinc than those found in meteorites.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p><p>Olivine is an abundant mineral, but gem-quality peridot is rather rare due to its <a href="/facts/Chemical_stability/j0YIgc6F">chemical instability</a> on Earth's surface. Olivine is usually found as small grains and tends to exist in a heavily weathered state, unsuitable for decorative use. Large crystals of <a href="/facts/Forsterite/Qg1HDy5q">forsterite</a>, the variety most often used to cut peridot gems, are rare; as a result, peridot is considered to be <a href="/facts/Precious_stone/kHffmvE3">precious</a>. </p><p>In the ancient world, the mining of peridot was called <i>topazios</i> then, on <a href="/facts/Zabargad_Island/VvVaAsBC">St. John's Island, in the Red Sea</a> began about 300 BCE.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>The principal source of peridot olivine today is the <a href="/facts/San_Carlos_Apache_Indian_Reservation/RaSCVczJ">San Carlos Apache Indian Reservation</a> in Arizona.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> It is also mined at another location in <a href="/facts/Arizona/6ayM3swJ">Arizona</a>, and in <a href="/facts/Arkansas/Qun124UP">Arkansas</a>, <a href="/facts/Hawaii/ImxFefeK">Hawaii</a>, <a href="/facts/Nevada/HNWhCrQv">Nevada</a>, and <a href="/facts/New_Mexico/wosJCGaW">New Mexico</a> at <a href="/facts/Kilbourne_Hole/vYycoNFg">Kilbourne Hole</a>, in the US; and in <a href="/facts/Australia/qLHpbppq">Australia</a>, <a href="/facts/Brazil/QHkG46GL">Brazil</a>, <a href="/facts/China/lTjIXY5p">China</a>, <a href="/facts/Egypt/8Ttg0JwB">Egypt</a>, <a href="/facts/Kenya/Y9Ko9pQu">Kenya</a>, <a href="/facts/Mexico/IT5bwhdh">Mexico</a>, <a href="/facts/Myanmar/zcqQH2oE">Myanmar</a> (Burma), <a href="/facts/Norway/wlDRKRTR">Norway</a>, <a href="/facts/Pakistan/cbIsvJy1">Pakistan</a>, <a href="/facts/Saudi_Arabia/uyUpe1J2">Saudi Arabia</a>, <a href="/facts/South_Africa/vvXQpLgq">South Africa</a>, <a href="/facts/Sri_Lanka/VtTBmysE">Sri Lanka</a>, and <a href="/facts/Tanzania/MJueJ7E4">Tanzania</a>. </p> <h3>In meteorites</h3> <p>Peridot crystals have been collected from some <a href="/facts/Pallasite/vYDf81Hl">pallasite</a> <a href="/facts/Meteorite/NsmHlBlX">meteorites</a>. The most commonly studied pallasitic peridot belongs to the Indonesian Jeppara meteorite, but others exist such as the Brenham, Esquel, Fukang, and Imilac meteorites.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Pallasitic (extraterrestrial) peridot differs chemically from its earthbound counterpart, in that pallasitic peridot lacks nickel.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h2 id="gemology">Gemology</h2> <p><a href="/facts/Orthorhombic/3zo4F8P0">Orthorhombic</a> minerals, like peridot, have <a href="/facts/Biaxial/xbmP4Yfy">biaxial</a> <a href="/facts/Birefringence/J4lLuR3a">birefringence</a> defined by three principal axes: α, β, and γ. Refractive index readings of faceted gems can range around α = 1.651, β = 1.668, and γ = 1.689, with a biaxial positive birefringence of 0.037–0.038. With decreasing magnesium and increasing iron concentration, the specific gravity, color darkness and refractive indices increase, and the β index shifts toward the γ index. Increasing iron concentration ultimately forms the iron-rich <a href="/facts/Endmember/ftb6zfhy">end-member</a> of the olivine <a href="/facts/Solid_solution/Mla7z8dc">solid solution</a> series <a href="/facts/Fayalite/UaPIeQRs">fayalite</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>A study of Chinese peridot gem samples determined the hydro-static <a href="/facts/Specific_gravity/ySquGd2x">specific gravity</a> to be 3.36 . The visible-light spectroscopy of the same Chinese peridot samples showed light bands between 493.0–481.0 nm, the strongest absorption at 492.0 nm.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p><p>The largest cut peridot olivine is a 310-<a href="/facts/Carat_(mass)/d2jIjtSs">carat</a> (62-gram) specimen in the gem collection of the <a href="/facts/Smithsonian_Museum/pqC74ta9">Smithsonian Museum</a> in Washington, D.C. </p><p>Inclusions are common in peridot crystals but their presence depends on the location where it was found and the geological conditions that led to its crystallization. </p> <ul><li>Primary negative crystals – rounded gas bubbles – form in situ with peridot, and are common in Hawaiian peridots.</li> <li>Secondary negative crystals form in peridot fractures.</li> <li>"Lily pad" cleavages are often seen in San Carlos peridots, and are a type of secondary negative crystal. They can easily be seen under reflected light as circular discs surrounding a negative crystal.</li> <li>Silky and rod-like inclusions are common in Pakistani peridots.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a></li> <li>The most common mineral inclusion in peridot is the chromium-rich mineral <a href="/facts/Chromite/DAWzm44Y">chromite</a>.</li> <li>Magnesium-rich minerals also can exist in the form of <a href="/facts/Pyrope/A0fdIhrs">pyrope</a> and <a href="/facts/Magnesiochromite/DAWzm44Y">magnesiochromite</a>. These two types of mineral inclusions are typically surrounded "lily-pad" cleavages.</li> <li>Biotite flakes appear flat, brown, translucent, and tabular.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li></ul> <h2 id="cultural-history">Cultural history</h2> <p>Peridot has been prized since the earliest civilizations for its claimed protective powers to drive away fears and nightmares, according to superstitions. There is a superstition that it carries the gift of "inner radiance", sharpening the mind and opening it to new levels of awareness and growth, helping one to recognize and realize one's destiny and spiritual purpose. </p><p>Peridot olivine is the <a href="/facts/Birthstone/y3hMc2TA">birthstone</a> for the month of August.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p><p>Peridot has often been mistaken for <a href="/facts/Emerald/pr52yTAD">emerald</a> <a href="/facts/Beryl/Fl7q1Hl9">beryl</a> and other green gems.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> Noted <a href="/facts/Gemologist/3bxqnE2b">gemologist</a> <a href="/facts/George_Frederick_Kunz/6Dywot6v">G.F. Kunz</a> discussed the confusion between <a href="/facts/Beryl/Fl7q1Hl9">beryl</a> and peridot in many <a href="/facts/Relic/oSksAgIf">church treasures</a>, most notably the "<a href="/facts/Shrine_of_the_Three_Kings/JcWlnx00">Three Magi</a> treasure" in the <a href="/facts/Cologne_Cathedral/uBjfSxgj">Dom</a> of <a href="/facts/Cologne/U2qmyGga">Cologne</a>, Germany.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a><a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> </p> <h2 id="gallery">Gallery</h2> <h2 id="footnotes">Footnotes</h2> <h2 id="external-links">External links</h2> Wikimedia Commons has media related to Peridot. <ul><li><a href="https://www.ganoksin.com/article/lets-talk-gemstones-peridot/">Ganoksin</a></li> <li><a href="https://www.mineralminers.com/html/perminfo.htm">Mineralminers</a></li> <li><a href="https://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/peridot.html">USGS peridot data</a></li> <li><a href="https://web.archive.org/web/20110808014635/http://www.emporia.edu/earthsci/amber/go340/peridot.htm">Emporia Edu</a></li> <li><a href="http://micro.magnet.fsu.edu/birthstones/pages/peridot.html">Florida State University – Peridot</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Peridot crystals: Formation & locations". Rock & Gem Magazine. 10 July 2023. Retrieved 21 January 2024 – via rockngem.com. Get to know this August birthstone <a href="https://www.rockngem.com/peridot-crystals/" target="_blank">https://www.rockngem.com/peridot-crystals/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Peridot". Gem notes. geo.utexas.edu. Geology Department. Austin, TX: The University of Texas. course 347k. Retrieved 2024-01-21. <a href="https://www.geo.utexas.edu/courses/347k/redesign/Gem_Notes/Peridot/peridot_main.htm" target="_blank">https://www.geo.utexas.edu/courses/347k/redesign/Gem_Notes/Peridot/peridot_main.htm</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Color, meanings, and symbolism [of] August birthstone peridot". Old Farmer's Almanac – via almanac.com. <a href="https://almanac.com/august-birthstone-color-and-meaning" target="_blank">https://almanac.com/august-birthstone-color-and-meaning</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Kuhn, Sherman M. (1982). "peridot". Middle English Dictionary. University of Michigan Press. p. 818 ff. ISBN 0-472-01163-4 – via Google books. <a href="0-472-01163-4" target="_blank">0-472-01163-4</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Ware, James, Sir (1705). The Antiquities and History of Ireland. A. Crook. p. 628 ff – via Google books.{{cite book}}: CS1 maint: multiple names: authors list (link) <a href="https://books.google.com/books?id=gjrnAAAAMAAJ&pg=PA628" target="_blank">https://books.google.com/books?id=gjrnAAAAMAAJ&pg=PA628</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Wise, Richard W. (2016). Secrets of the Gem Trade: The connoisseur's guide to precious gemstones (2nd ed.). Lenox, MA: Brunswick House Press. p. 220. ISBN 9780972822329. <a href="9780972822329" target="_blank">9780972822329</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Knafelc, Joseph; Filiberto, Justin; Ferré, Eric C.; Conder, James A.; Costello, Lacey; Crandall, Jake R.; et al. (May 2019). "The effect of oxidation on the mineralogy and magnetic properties of olivine". American Mineralogist. 104 (5): 694–702. Bibcode:2019AmMin.104..694K. doi:10.2138/am-2019-6829. ISSN 0003-004X. S2CID 155508562 – via geoscienceworld.org. <a href="https://pubs.geoscienceworld.org/ammin/article-abstract/104/5/694/570176/The-effect-of-oxidation-on-the-mineralogy-and" target="_blank">https://pubs.geoscienceworld.org/ammin/article-abstract/104/5/694/570176/The-effect-of-oxidation-on-the-mineralogy-and</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Shen, A.; et al. (2011). "Identification of extraterrestrial peridot by trace elements". Gems & Gemology. 47 (3): 208–213. doi:10.5741/GEMS.47.3.208. <a href="/wiki/Gems_%26_Gemology" target="_blank">/wiki/Gems_%26_Gemology</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"St. John's Island peridot information and history". Mindat.org. <a href="http://www.mindat.org/loc-6423.html" target="_blank">http://www.mindat.org/loc-6423.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Although some good olive-colored crystals are found in a few other places, like Burma, China, Zambia, and Pakistan, ninety percent of all known peridots are found in just one place. It is a Native American reservation, and it is located in a little-visited corner of the United States: San Carlos." — V. Finlay[10][full citation needed] <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Leelawatanasuk, Thanong; Atichat, Wilawan; Thye Sun, Tay; Sriprasert, Boontawee; Jakkawanvibul, Jirapit (2014). "Some characteristics of taaffeite from Myanmar". The Journal of Gemmology. 34 (2): 144–148. doi:10.15506/jog.2014.34.2.144. ISSN 1355-4565. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Alien sightings: Pallasite" (PDF). stonegrouplabs.com. <a href="https://stonegrouplabs.com/wp-content/uploads/2021/06/0314GG-MarAprGMNPallasite.pdf" target="_blank">https://stonegrouplabs.com/wp-content/uploads/2021/06/0314GG-MarAprGMNPallasite.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Koivula, John I. (1981). "San Carlos peridot" (PDF). Gems & Gemology. 17 (4): 205–214. doi:10.5741/gems.17.4.205. Retrieved 14 February 2023 – via gia.edu. <a href="https://www.gia.edu/doc/San-Carlos-Peridot.pdf" target="_blank">https://www.gia.edu/doc/San-Carlos-Peridot.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Koivula, John I.; Fryer, C.W. (1 April 1986). "The gemological characteristics of Chinese peridot". Gems & Gemology. 22 (1): 38–40. doi:10.5741/GEMS.22.1.38. ISSN 0016-626X. <a href="http://www.gia.edu/gems-gemology/spring-1986-china-peridot-koivula" target="_blank">http://www.gia.edu/gems-gemology/spring-1986-china-peridot-koivula</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"Sapat Gali, Naran, Kaghan Valley, Mansehra District, Khyber Pakhtunkhwa Province, Pakistan". mindat.org. <a href="https://www.mindat.org/loc-2536.html" target="_blank">https://www.mindat.org/loc-2536.html</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>"Biotite as inclusions". Dictionary of Gems and Gemology. Springer. 2009. p. 87. doi:10.1007/978-3-540-72816-0_2288. ISBN 978-3-540-72795-8. <a href="978-3-540-72795-8" target="_blank">978-3-540-72795-8</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>"Birthstones for each month". gia.edu. Gemological Institute of America. Retrieved 5 February 2021. <a href="https://www.gia.edu/birthstones" target="_blank">https://www.gia.edu/birthstones</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>"Peridot gem guide and properties chart". Gemstones.com. Retrieved 2022-09-14. <a href="https://www.gemstones.com/gemopedia/peridot" target="_blank">https://www.gemstones.com/gemopedia/peridot</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Kunz, G.F. (June 1971). The Curious Lore of Precious Stones. New York, NY: Dover Publications. p. 66. ISBN 0-486-22227-6. <a href="0-486-22227-6" target="_blank">0-486-22227-6</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>"Peridot crystals: Formation & locations". Rock & Gem Magazine. 10 July 2023. Retrieved 21 January 2024 – via rockngem.com. Get to know this August birthstone <a href="https://www.rockngem.com/peridot-crystals/" target="_blank">https://www.rockngem.com/peridot-crystals/</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> </ol>