File:Large potassium feldspar & quartz crystals in pegmatitic granite (Ruggles Pegmatite, Devonian; Ruggles Pegmatite Mine, New Hampshire, USA) 1 (8290570829).jpg
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[edit]DescriptionLarge potassium feldspar & quartz crystals in pegmatitic granite (Ruggles Pegmatite, Devonian; Ruggles Pegmatite Mine, New Hampshire, USA) 1 (8290570829).jpg |
Huge whitish-gray quartz crystal (left) & tan-colored potassium feldspar crystal (right) in pegmatitic granite in the Devonian of New Hampshire, USA. (geology hammer for scale) Spectacular mineral collecting can be had at the Ruggles Pegmatite Mine near Grafton, New Hampshire, USA. The Ruggles Mine started off in the early 1800s as a muscovite mica mine, but it's now a tourist site. Its walls have beautiful exposures of a mid-Paleozoic granite pegmatite, having unbelievably large crystals. Well over 100 minerals have been reported from this pegmatite, but the most common rock-forming minerals here are quartz, potassium feldspar, biotite mica, muscovite mica, and schorl tourmaline. The Devonian-aged pegmatite at Ruggles Mine is one of several in the Grafton Pegmatite Field. These intrusions are part of the New Hampshire Plutonic Series, emplaced during the Acadian Orogeny. The large quartz and potassium feldspar crystals shown above well demonstrate the very coarsely-crystalline nature of pegmatites. Pegmatitic texture refers to an intrusive igneous rock having all or almost all crystals larger than 1 centimeter. Most pegmatitic-textured igneous rocks have a granitic composition, and so are called pegmatitic granites or granite pegmatites, or just "pegmatites". Pegmatites tend to form in the margins of cooling batholiths, during the final stages of a crystallization. After most of the magma has crystallized, the residual magma is rich in gas & water & silica & incompatible ions (atoms too large or too small to fit in “normal” minerals that formed earlier). Cooling of such residual magma results in pegmatites. The water-rich nature of this residual magma allows rapid ion transport during crystallization, resulting in very large crystals. The incompatible ions tend to form unusual minerals and “garbage can” minerals (e.g., beryl, chrysoberyl, columbite/tantalite, uraninite, cryolite, monazite, apatite, lepidolite, spodumene, zoisite, topaz, zircon, molybdenite, etc.). Locality: Ruggles Pegmatite Mine, near Grafton, southern Grafton County, western New Hampshire, USA |
Date | |
Source | Large potassium feldspar & quartz crystals in pegmatitic granite (Ruggles Pegmatite, Devonian; Ruggles Pegmatite Mine, New Hampshire, USA) 1 |
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@N05/8290570829 (archive). It was reviewed on 12 November 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
12 November 2019
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current | 04:15, 12 November 2019 | 960 × 720 (520 KB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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Height | 720 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 96 dpi |
Vertical resolution | 96 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 15:57, 17 September 2017 |
Exif version | 2.21 |
Color space | sRGB |
Unique ID of original document | A1CCDA431D154D18DDBED4FB7B7750E4 |
Date and time of digitizing | 11:55, 17 September 2017 |
Date metadata was last modified | 11:57, 17 September 2017 |