Plagioclase
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Description
A common series of feldspars that contain both calcium and sodium aluminum silicates. Placiogclase minerals fall in between the categories of Albite (sodium aluminum silicate) and Anorthite (calcium aluminum silicate). Examples of plagioclase minerals are: Labradorite, and sunstones. Some rocks that contain plagioclase minerals are: andesite, Basalt, Diabase, Diorite, and Gabbro.
Synonyms and Related Terms
soda lime feldspar; oligoclase; labradorite; bytownite; plagioclase (Port.);
Physical and Chemical Properties
Good cleavage in two directions. Fracture = uneven. Luster = vitreous. Streak = white
| Mohs Hardness | 6.0-6.5 |
|---|---|
| Density | 2.62-2.76 |
| Refractive Index | 1.53-1.59 |
Comparisons
Properties of Common Gemstones
Resources and Citations
- Mineralogy Database: Plagioclase
- Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
- Encyclopedia Britannica, http://www.britannica.com "plagioclase." Accessed 9 Dec. 2004 .
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998