Lazuritic-pyritic marble (Sar-e-Sang Deposit, Sakhi Formation, Precambrian, 2.4-2.7 Ga (?); Sar-e-Sang Mining District, Hindu-Kush Mountains, Afghanistan) 1 : 無料・フリー素材/写真
Lazuritic-pyritic marble (Sar-e-Sang Deposit, Sakhi Formation, Precambrian, 2.4-2.7 Ga (?); Sar-e-Sang Mining District, Hindu-Kush Mountains, Afghanistan) 1 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Lazuritic-pyritic marble from the Precambrian of Afghanistan. (~3.25 centimeters across at its widest)Blue = lazuriteWhitish = calciteBrassy gold specks = pyriteLapis lazuli is a beautiful and rare metamorphic rock that's been valued as a gemstone for thousands of years. The highest-quality lapis lazuli deposit on Earth is in northeastern Afghanistan. The name "lapis lazuli" is Latin and Persian for “heaven stone”, or “sky stone”, or “blue stone”. Lapis lazuli is dominated by the deep-blue mineral lazurite, which is a sodalite-group feldspathoid - (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2. Commonly, whitish calcite (CaCO3) and brassy-colored pyrite (FeS2) are present. In this sample, the calcite component is probably high enough to call it a lazuritic-pyritic marble. Lazurite is one of the most intensely-blue mineral known. The intensity of the blue color in lazurite has been attributed to the sulfur and calcium content. Lapis lazuli is known from elsewhere in the world, but northeastern Afghanistan is the classic locality, where it has been reportedly mined for at least 7000 years. In ancient times, lapis lazuli was referred to as “sapphire”. Pliny the Elder's 37-volume work Naturalis Historiae ("Natural History"), written in the ~70s A.D., refers to Afghani lapis lazuli as “sappiri”, and notes that it has glistening dots of gold in it - see his book 37. Afghani lapis lazuli comes from the Sar-e-Sang Deposit, a ~1 to 8 meter thick and ~20 to 450 meter long occurrence consisting of north-south trending veins, lenses, and layers of lapis lazuli within marble. Stratigraphically, this is the Precambrian-aged Sakhi Formation. The lapis lazuli rocks in this area formed under complex metamorphic conditions, apparently including high-grade, prograde metamorphism and retrograde metamorphism (Turner & Groat, 2022). Precursor rocks were limestones and evaporites.The lapis lazuli mines of northeastern Afghanistan are some of the most difficult-to-access localities in the world, occurring along steep slopes of deeply carved, narrow river canyons in the Hindu-Kush Mountains. The Sar-e-Sang Mining District occurs about 1500 feet above the water level of the Sar-e-Sang River (a west-flowing tributary of the Kokcha River). Mine access is only via narrow foot trails. Regarding this area, British Army Lieutenant John Wood famously said in 1837: “If you do not wish to die, avoid the Valley of Kokcha.”Stratigraphy: marble member, Sakhi Formation, Anglich Group, Sar-e-Sang Series, Late Archean to early Paleoproterozoic (?), ~2.4 to 2.7 Ga metamorphic date (the chronometric age comes from dating inferred correlative rocks in Pamir in adjacent Tajikhistan)Geologic context: eastern limb of the Kokcha Anticline, Fayzabad Metamorphic Massif, South Badakhshan BlockLocality: Sar-e-Sang Mining District, above the lowermost reaches of the Sar-e-Sang River, northern Kuran Wa Munjan District, southern Badakhshan Province, northern flanks of the western Hindu-Kush Mountains, northeastern Afghanistan (the Sar-e-Sang Mine adits are apparently in the vicinity of 36° 12.2’ to 36° 14.14’ North latitude, 70° 47.85’ to 70° 48.63’ East longitude)------------------------Reference cited:Turner, D. & L.E. Groat. 2022. Geology and Mineralogy of Gemstones. American Geophysical Union & John Wiley and Sons, Incorporated. Washington D.C. & Hoboken, New Jersey. 268 pp. |
| 撮影日 | 2025-03-03 12:13:35 |
| 撮影者 | James St. John |
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