File:Quartz crystal-lined vug with barite in flint meganodule (Vanport Flint, Middle Pennsylvanian; Nethers Flint Quarries, eastern Flint Ridge, Ohio, USA) 4 (23581500510).jpg
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[edit]DescriptionQuartz crystal-lined vug with barite in flint meganodule (Vanport Flint, Middle Pennsylvanian; Nethers Flint Quarries, eastern Flint Ridge, Ohio, USA) 4 (23581500510).jpg |
Quartz crystal-lined vug with barite in flint meganodule in the Pennsylvanian of Ohio, USA. Flint is the "official" state gemstone of Ohio. "Flint" is sometimes used as a lithologic term by modern geologists, but it is a synonym for chert. Flint and chert are the same - they are cryptocrystalline, quartzose sedimentary rocks. Rockhounds often assert that flint is high-quality while chert is low-quality. Some geologists assert that "flint" implies a biogenic origin and "chert" implies a chemical origin. Many cherts do have a chemical origin - chert nodules are moderately common in some limestone units. The nodules form during diagenesis - pre-existing silica components in the carbonate sediments are dissolved, mobilized, and reprecipitated as chert masses. Some cherts do have a biogenic origin - for example, radiolarian cherts (rich in radiolarian microfossils) or spicular cherts (rich in siliceous sponge spicules). The most famous flint deposit in Ohio is Flint Ridge, in Licking County. At this locality, the Middle Pennsylvanian-aged Vanport Flint is exposed in several places. The geologic literature on the Vanport Flint is relatively sparse, with inaccurate & incomplete descriptions and characterizations. For example, the literature describes the Vanport as a sheet of flint at Flint Ridge - it's actually a meganodule horizon. Other descriptions refer to the chert as the remains of siliceous sponges. In reality, siliceous sponge spicules are quite scarce in Vanport samples. Two graduate student projects during the 2000s, conducted at two different universities, had very different conclusions & interpretations about the origin of the Vanport Flint. A 2003 study concluded that chert at Flint Ridge is biogenic in origin. A 2006 study concluded that the chert is chemical in origin. Studies done by geologists at Ohio State University at Newark indicate that the Vanport Flint has a relatively complex history, the details of which are still being worked out. Modern flint knappers value the Vanport Flint for being multicolored and high-quality (= very few impurities). With artificial heating, the flint is more easily knapped into arrowheads, spear points, and other objects. Prehistoric American Indians quarried the Vanport Flint at many specific sites on Flint Ridge. Old Indian flint pits can be examined along hiking trails in Flint Ridge State Park ("State Memorial"). Many authentic Indian artifacts found in Ohio (arrowheads & spearpoint - "projectile points") are composed of Vanport Flint. The above photo shows an outcrop of a flint meganodule in a small flint pit on the eastern side of Flint Ridge. The cavity is a quartz crystal-lined vug. This particular pit is relatively new and the vug was only recently exposed. Loose pieces of barite partially filled the cavity before they were collected (a couple loose pieces are still present on the floor of this vug). Barite is barium sulfate - BaSO4. It has a nonmetallic luster, a clearish to whitish color with white streak, is noticeably heavy for its size, and has rhombohedral cleavage. Barite is a scarce mineral in the Vanport Flint at Nethers Flint Quarries, but it has been found in-situ in vugs like this - sometimes lined with quartz crystals and sometimes not. Barite has also been found as small to moderately large loose pieces in rock/dirt piles adjacent to excavated flint pits. Stratigraphy: Vanport Flint, Allegheny Group, upper Middle Pennsylvanian Locality: Nethers Flint Quarries - flint pits in the woods on the southwestern side of Flint Ridge Road, eastern Flint Ridge, far-western Muskingum County, east-central Ohio, USA (GPS: 40° 00.137’ North latitude, 82° 11.544’ West longitude) |
Date | |
Source | Quartz crystal-lined vug with barite in flint meganodule (Vanport Flint, Middle Pennsylvanian; Nethers Flint Quarries, eastern Flint Ridge, Ohio, USA) 4 |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/23581500510 (archive). It was reviewed on 12 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
12 October 2019
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current | 06:23, 12 October 2019 | 4,000 × 3,000 (3.77 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Camera manufacturer | Canon |
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Date and time of data generation | 15:43, 13 December 2015 |
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Image title | |
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Horizontal resolution | 180 dpi |
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File change date and time | 19:22, 20 December 2015 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 15:43, 13 December 2015 |
Meaning of each component |
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Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 12:22, 20 December 2015 |
Unique ID of original document | 8301F8C05CD3C934789E696EA580C2AF |