File:Corundite_(emery_rock)_slabbed_Naxos_Emery_Deposits.jpg
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Summary
DescriptionCorundite (emery rock) slabbed Naxos Emery Deposits.jpg |
Corundite (emery rock) (cut, wet surface, 10.0 cm across) with blue corundum/sapphire and yellowish-brown calcite. The bluish-brownish corundite is a fracture filling. The host rock can be seen on the left side of the specimen - a chloritoid-hematite-rich diasporite (dark green = chloritoid; red spots = hematite). Corundite is a remarkable metamorphic rock. The sample shown here has an attractive bluish color and wisps of yellow-brown. Its composition and origin are quite unusual. Corundite (a.k.a. emery rock) is dominated by corundum, a very hard (H ≡9) aluminum oxide mineral (Al2O3). This particular rock has blue corundum, therefore it can be called sapphire. Rock-forming corundum is rare. This material comes from the Naxos Emery Deposits on the island of Naxos in the Aegean Sea. Naxos is dominated by metamorphic rocks and some igneous rocks. Much of the island consists of marbles (originally limestones). Some of the original limestones had lenses of bauxite, which is a rock having aluminum hydroxy-oxide minerals. Upon metamorphism, the limestones were converted to marbles and the bauxites were converted to diasporites (= diaspore (AlO·OH)-dominated rocks) (= very dark green area on the left side of the first photo). Upon further metamorphism, the diasporites were converted to corundites plus water. High fluid pressures fractured the rocks, and the fractures got filled up with corundite. Metamorphism on Naxos occurred during the Cenozoic in two main phases. A high-grade metamorphic event occurred during the Eocene, at about 40-50 million years ago. A second, intermediate-grade metamorphic event occurred during the Early Miocene, at 16-20 million years ago. Info. synthesized from: Urai & Feenstra (2001) - Weakening associated with the diaspore-corundum dehydration reaction in metabauxites: an example from Naxos (Greece). Journal of Structural Geology 23: 941-950. Feenstra & Wunder (2002) - Dehydration of diasporite to corundite in nature and experiment. Geology 30(2): 119-122. |
Date | |
Source | Corundite (emery rock) (Naxos Emery Deposits, metamorphism in the Eocene & Miocene, 40-50 Ma & 16-20; Naxos Island, Aegean Sea) 1 |
Author | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/15068443932. It was reviewed on 30 August 2014 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
30 August 2014
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28 August 2014
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 01:19, 30 August 2014 | 1,693 × 823 (1.41 MB) | Tillman | Transferred from Flickr via Flickr2commons |
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Pixel composition | RGB |
---|---|
Orientation | Normal |
Horizontal resolution | 425 dpi |
Vertical resolution | 425 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 22:28, 28 August 2014 |
Color space | Uncalibrated |
Image width | 1,693 px |
Image height | 823 px |
Date and time of digitizing | 18:24, 28 August 2014 |
Date metadata was last modified | 18:28, 28 August 2014 |