File:Fossil pearls (Pliocene or Pleistocene; Florida, USA).jpg
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Summary
[edit]DescriptionFossil pearls (Pliocene or Pleistocene; Florida, USA).jpg |
English: Fossil pearls from the upper Cenozoic of Florida, USA. (the long axis of the largest specimen is 1.2 centimeters)
Pearls are spherical to subspherical to irregularly-shaped, biogenic concretions of slightly iridescent, nacreous aragonite (CaCO3 - calcium carbonate). Pearls are principally made by pearl oysters (Animalia, Mollusca, Bivalvia). Natural pearls are scarce. Well-formed, spherical natural pearls are rare. Fossil pearls are known, but are also scarce. "Mother of pearl" is relatively common - the same material in pearls occurs in the actual shells of some bivalves. Well-known pearl oysters include Pinctada margaritifera (the black-lipped pearl oyster), Pinctada fucata (the Japanese pearl oyster), and Pinctada maxima (the gold-lipped pearl oyster). Mother-of-pearl is well developed in shells of other species such as Pinctada imbricata (Atlantic pearl oyster), Pteria colymbus, Pteria penguin (both are winged pearl oysters), Haliotis spp. (abalones), and Atrina spp. (pen shells). Natural pearls form when foreign objects, such as sediment grains or other debris, enter a pearl oyster and get embedded in its mantle tissue. The particle is slowly coated with nacreous aragonite, which prevents the particle from causing disease or injury. The end result is a biogenic concretion called a pearl. Natural pearls show a concentric structure through the entire cross-section. Almost all commercially available pearls are semi-natural - they have been cultured. Cultured pearls have been available for many decades. A spherical bead is placed inside a pearl oyster, under its mantle tissue. The bead is slowly coated with nacreous aragonite to produce a cultured pearl, which shows concentric structure only in the outer portions of its cross-section. Marine pearls can be whitish, pinkish, yellowish, or blackish. Freshwater pearls are also known - natural examples vary from ~spherical to highly irregularly-shaped. Blister pearls are attached to the host mollusc's shell. Stratigraphy: undetermined stratigraphic unit, Pliocene or Pleistocene Locality: unrecorded/undisclosed site in Florida, USA |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/48609221078/ |
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@N05/48609221078 (archive). It was reviewed on 20 February 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
20 February 2020
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current | 19:23, 20 February 2020 | ![]() | 2,143 × 1,347 (1.48 MB) | Ser Amantio di Nicolao (talk | contribs) | User created page with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/11 |
ISO speed rating | 80 |
Date and time of data generation | 19:40, 23 August 2019 |
Lens focal length | 11.614 mm |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 16.0 (Macintosh) |
File change date and time | 21:45, 23 August 2019 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 19:40, 23 August 2019 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.90625 |
APEX exposure bias | −0.33333333333333 |
Maximum land aperture | 4 APEX (f/4) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 17:45, 23 August 2019 |
Unique ID of original document | ADB0F0AF03A8D514EF314BA947EE568F |
IIM version | 24,576 |