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MINERALS INDEX
Phlogopite |
| Formula complex |
| Monoclinic |
Mica of golden-brown, yellow, and white tints is widely disseminated in the Franklin limestone, and wherever tested it has been found to have a small optical axial angle. Hence it is regarded as phlogopite, although chemical evidence is lacking.
Very perfect pyramidal crystals of such mica, some of them more than 4 inches long, were seen in the Canfield collection, and one of them is illustrated in plate 18, A. They were found in the limestone near Franklin, the best of them near the Catholic Church (locality 12, plate 1). A specimen in the same collection showed mica with a greenish metallic sheen on the cleavage due to paper-thin enclosures of epidote. Beautifully formed but small crystals of phlogopite are abundant in the limestone at Rudeville, as, indeed, in most of the limestone quarries of the region.
Abundant large and well-formed crystals of phlogopite, quite comparable in quality to any seen in the local collections, were found in 1910 in the large Fowler limestone quarry. They are generally embedded in calcite, which separates very cleanly from them, but in a few specimens the embedding matrix was pure-white fluorite in coarsely cleavable masses.
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© by Herb Yeates 1997-2001.
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page created: January 12, 2001 6:45 PM
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