See the owners introduction to Table Mountain, Oregon nepheline project and research.
The Table Mountain nepheline has a Mohs Scale hardness of 6, a specific gravity of 2.57, and an average weight of 160 pounds per cubic foot. U. S. Geological Survey Professional Paper 840, and the State of Oregon Department of Geology & Mineral Industries Bulletin 8, show that the unprocessed material from Table Mountain consists of:
SiO2 (silica) 59.62%
AL2O3 (alumina)18.60%
Fe2O2 (Ferric Oxide) 02.86%
The composition of commercially processed Grade A nepheline is:
SiO2 (silica) 60.04%
AL2O3 (alumina) 23.06%
Fe2O2 (ferric oxide) 00.08%
Supposedly a limiting factor in utilizing the Table Mountain material, as is, in the production of clear glass and ceramic items has been the high iron content. The discoloration caused by the iron is not a factor in beer and wine bottles. Recent mill tests show the removal of iron not to be a problem at all. And a higher iron content has been shown to be desirable in roofing granules in that the "impurity" filters UV rays.
The main competitor in North America, the Blue Mountain, Ontario deposit owned by Indusmin Ltd, operates on raw material that contains 2% ferric oxide. After processing, this "waste" is sold as 56% Fe.
Besides the iron content, other factors limiting utilization of the Table Mountain material such as rock wool, and alumina, and extenders only seem to be location, and the initial cost of developing production. The material, due to the size of blocks and hardness of the rock, makes a good jettystone.
And, as the light to medium gray (with a blue tint) granite-like rock takes a good polish, displaying a soft cloud-like effect, nepheline syenite material is a desirable dimension stone for building facing, memorials, and floor tiles. The Audubon Society Field Guide to North American Rocks and Minerals states that the nepheline syenite quarried at Magnet Cove, Arkansas, is "an excellent building stone."
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