Nepheline syenite

Refractive Index 1.53-1.55 Specific Gravity 2.57 Mohs Hardness 5.5-6 

Refractive Index 1.52-1.54 Specific Gravity 2.54-2.57 Mohs Hardness 6 

Refractive Index 1.53-1.54 Specific Gravity 2.62 Mohs Hardness 6 

Nepheline syenite is characterized primarily by chemistry and particle size. 

Ceramic grade - Grades for ceramics are finely groimd (typically 200, 270, or 400 mesh), controlled for PCE (pyrometric cone equivalent), free of dark impurities, and white-firing without specking. 

---

The actual name dry scrubbing was first publicized by Teller [U.S. Patent no. 3,721,066 (1973)]. He worked both with classical Army-type soda-lime and with his patented water-activated form of the alkaline feldspar nepheline syenite as a flow agent and feedstock sorbent for HF and SO9 in hot, sticky fumes from glass melting furnaces. He claimed capture of more than 99 percent of 180 ppm HF and SO9 for more than 20 hours in a packed bed of 200 X 325 mesh hydrated nephehne syenite at 42,000/hr. 

Aegiiine NaFeSi206 Nepheline syenites hypersodic granites... 

The IRAC can be intrusive subunits, emplacement these feldspar-free layered mafic (LMSC), (2) a large carbonatite lens, (3) a zoned nepheline syenite sub-complex (ZSSC), and (4) a dyke suite consisting of syenitic dykes, carbonatites, and alkaline... 

The contacts between lamprophyres and the IRAC range from planar to very irregular. The lamprophyres typically exhibit a chilled margin. However, at both the hand sample and thin-section scale, a sannaite lamprophyre sample exhibits a cuspate boundary against a nepheline syenite dyke, indicative of two partially molten materials. Lamprophyre dykes cross-cutting syenitic dykes have also been observed. 

Based on mineralogical and textural similarities (supported by geochemistry), the rocks of the syenitic dyke swarm can be subdivided into three groups (1) nepheline syenite - nephelinolite group (NS-N), (2) syenite - monzodiorite group (SM), and (3) an alkali feldspar granite dyke. 

The rocks of the NS-N dyke group range from nepheline syenite to sodalite-bearing nephelinolite. The primary phases in the NS-N dyke group are k-feldspar and nepheline, with variable abundances of amphibole, plagioclase, phlogopite, calcite, sodalite, titanite, cancrinite, apatite, clinopyroxene, zircon, chlorite, quartz, pyrochlore, and opaque phases. 

In parallel Canada also pioneered work on the immobilization of radioactive wastes into glass (vitrification) for permanent disposal. (O A natural mineral, nepheline syenite, was used as the basic material because it produced a glass with excellent... 

Hafnium had lain hidden for untold centuries, not because of its rarity but because of its dose similarity to zirconium (16), and when Professor von Hevesy examined some historic museum specimens of zirconium compounds which had been prepared by Julius Thomsen, C. F. Rammelsberg, A. E. Nordenskjold, J.-C. G. de Marignac, and other experts on the chemistry of zirconium, he found that they contained from 1 to 5 per cent of the new element (26, 27). The latter is far more abundant than silver or gold. Since the earlier chemists were unable to prepare zirconium compounds free from hafnium, the discovery of the new element necessitated a revision of the atomic weight of zirconium (24, 28). Some of the minerals were of nepheline syenitic and some of granitic origin (20). Hafnium and zirconium are so closely related chemically and so closely associated in the mineral realm that their separation is even more difficult than that of niobium (columbium) and tantalum (29). The ratio of hafnium to zirconium is not the same in all minerals. 

Sphene is an accessory mineral of widespread occurrence in igneous rocks, and calcium-rich schists and gneisses of metamoiphic origin, and very common in nepheline-syenites. In the United States sphene is found in Arkansas, California, New Jersey, New York in Ontario and Quebec in Canada and from Greenland, Brazil, Norway, France, Austria, Finland, Russia, Madagascar and New Zealand, as well as many other world localities. 

In some countries, feldspars are replaced by nepheline syenites containing the mineral nepheline (Na20. AljOj. 2 S1O2) accompanied by albite, microcline, kaliophillite (K2O. AI2O3.2 Si02), etc. This contains less S1O2 and more alkalis, in particular Na20. 

An example of the composition of potassium feldspar and that of a nepheline syenite (wt. %) is ... 

Nepheline syenite an alkali-rich, silica-depleted igneous rock emplaced below the earth s surface. 

---