Minerals alunite

The model calculated in this manner predicts that two minerals, alunite [KA13(0H)6(S04)2] and anhydrite (CaSC>4), are supersaturated in the fluid at 175 °C, although neither mineral is observed in the district. This result is not surprising, given that the fluid s salinity exceeds the correlation limit for the activity coefficient model (Chapter 8). The observed composition in this case (Table 22.1), furthermore, actually represents the average of fluids from many inclusions and hence a mixture of hydrothermal fluids present over a range of time. As noted in Chapter 6, mixtures of fluids tend to be supersaturated, even if the individual fluids are not. 

The mineral alunite, and its iron equivalent jarosite, is a special case. Alunite (KAl2(S02)2(OH)2) contains four sites where elements containing stable isotopes are found and both the sulfate and hydroxyl anionic groups may provide information on fluid source and condition of formation. 

It occurs in nature in minerals alunite, KAl3(S04)2(0H)6 and natroalunite, NaAl3(S04)2(0H)6. The anhydrous salt is used in food applications. 

Al-rich minerals Alunite Amorphous Crystalline Alunogen Basaluminite Amorphous Crystalline Halotrichite Pickcringite... 

ALUNITE. The mineral alunite, KAl3(S04)2(0H)t , is a basic hydrous sulfate of aluminum and potassium a variety called natroalunite is rich in soda. Alunite crystallizes in the hexagonal system and forms rhombohedrons with small angles, hence resembling cubes. It may be in fibrous or tabular forms, or massive. Hardness, 3.5-4 sp gr, 2.58-2.75 luster, vitreous to pearly streak white transparent to opaque brittle color, white to grayish or reddish,... 

The best native source for this is the mineral Alunite (or Alum stone) which is ground and roasted, then dissolved in water. After filtration, the water is evaporated to obtain crystals of Alum. 

Aluminum potassium sulfate occurs naturally in the form of the minerals alunite and kalinite. Where these minerals are available, the compound can be mined and purified to obtain potash alum. Where the minerals are not available, the compound can be produced synthetically by combining aqueous aluminum sulfate with aqueous potassium sulfate. The two compounds react with each other in solution to form the double salt, aluminum potassium sulfate, which can then be extracted by allowing the solutions to evaporate, during which the desired compound crystallizes out. 

The CAS registry Hsts 5,037 aluminum-containing compounds exclusive of alloys and intermetaUics. Some of these are Hsted in Table 1. Except for nepheline and alunite in the USSR and Poland, bauxite is the raw material for all manufactured aluminum compounds. The term bauxite is used for ores that contain economically recoverable quantities of the aluminum hydroxide mineral gibbsite or the oxide—hydroxide forms boehmite and diaspore. 

Potassium alum is manufactured by treating bauxite with sulfuric acid and then potassium sulfate. Alternatively, aluminum sulfate is reacted with potassium sulfate, or the mineral alum stone, alunite, can be calciaed and leached with sulfuric acid. Alunite is a basic potassium aluminum sulfate... 

Advanced arigillic alteration is found at the upper horizon than the sites of potassic and intermediate argillic alterations where the Au-Ag mineralization occurs (e.g., Seigoshi, Yatani, Kushikino, Hishikari). This type of alteration takes blanket-form in upper part and vein-form in lower part (Iwao, 1962 Shikazono, 1985a). The conspicuous zonation from upper to lower horizon is known at the Ugusu silica deposit, namely, silica zone, alunite zone, kaolinite zone and montmorillonite zone (Iwao, 1949, 1958, 1962). 

If alunite, K-mica and kaolinite (which are common minerals in the advanced argillic alteration) are in equilibrium, the concentration of H2SO4 can be estimated based on the experimental work by Hemley et al. (1969) the concentration of H2SO4 at 200°C and 300°C is 0.002 and 0.012 M, respectively. This may suggest that it is difficult to form such a high concentration of sulfate ion only by oxidation of H2S. 

This type of mixing could reasonably explain the occurrence of acidic alteration minerals such as kaolinite and alunite in the low-sulfidation epithermal gold vein district (e.g., Seta in northeast Hokkaido, Hishikari in southern Kyushu) (Yajima et al., 1997)... 

Berger, B.R. (1983b) Epithermal gold, quartz-alunite type. In Cox, D.P. (ed.), GEOMINAS Mineral Resource Assessment of Columbia — Ore Deposit Models, U.S. Geological Survey, Open-File Report, 83, v. 23, 40-41. 

Polyak VJ, McIntosh WC, Provencio P, Giiven N (1998) Age and Origin of Carlsbad Caverns and related caves from " °Ar/ Ar of alunite. Science 279 1919-1922 Porcelli D, Swanzenski PW (2003)The behavior of U- and Th- series nuclides in groundwater. Rev Mineral Geochem 52 317-361... 

In our initial use of VIRS methods, we have chosen a diverse set of projects. These include epithermal-style precious metal mineralization (eastern and central Newfoundland), mesothermal gold mineralization (Central Newfoundland), syngenetic VMS mineralization and related alteration (Central Newfoundland), porphyry-style Mo-Cu mineralization (southern Newfoundland) and uranium mineralization in the Central Mineral Belt of Labrador. Space does not permit detailed discussion of results, but in all cases we were able to recognize distinctive alteration species and document their distribution. In some cases, results provided surprises, eg., the recognition of topaz in quartz-alunite alteration and possible Li-rich micas in VMS alteration influenced by magmatic fluids. In some cases, the resolution of species in mixed assemblages proved to be difficult, but the overall spectral patterns could still be used to discriminate alteration facies and demonstrate their superposition. 

Products resulting from the decay of organic matter—e.g. Indian nitre and South African nitre. The value of saltpetre for the manufacture of gunpowder and in the chemical industries is greatly in excess of its value as a fertilizer and consequently nitre is not usually regarded as a source of potash supply. (6) Blast furnace and cement-kiln dust. (7) The insoluble potash minerals—e.g. felspar, alunite, leucite, etc. 

Numerous processes have been proposed for extracting potash from felspar, leucite, alunite, and other minerals rich in this substance, but the cost is so great that very few proposals yet made ofier promise of successful competition with the Stassfurt deposits. This is even the case with alunite, where mere calcination to 1000° drives off water and sulphuric acid, leaving water-soluble potassium sulphate, and alumina. Humphry Davy in his paper On Some Chemical Agencies of Electricity (1807), indicated in Cap. Ill, found that when water was electrolyzed in cavities contained in celestine, fluorspar, zeolite, lepidolite, basalt, vitreous lava, agate, or glass, the bases separated from the acid and accumulated about the cathode. It is therefore probable that if water with finely divided potash minerals in suspension were electrolyzed, the alkali would be separated in a convenient simple way. 

Menchetti, S. Sabelli, C. (1976) Crystal chemistry of the alunite series Crystal structure refinement of alunite and synthetic jarosite. Neues Jahrb. Mineral. Mh, pp. 406-17. 

The presence of sulfate in water can alter the solubilities of gibbsite and kaolinite, wo minerals considered to control the concentration of aluminum in natural waters, lius, minerals of lesser solubilities control the aluminum concentration in acid sulfate vaters. These minerals most likely are alunogen [Al2(SO4)317H20s], with a Ksp of 0"7 alunite [KA13(S04)2(0H)6s], with a Ksp of KT85 4 jurbanite [AKSO OH)-... 

Twelvefold coordination of lower valence actinides is inferred only for the orthophosphate mineral eylettersite, (Th,Pb)i.xAl3(P04,Si04)2(0H)6 [77], which is a member of the alunite-jarosite supergroup that includes the isotypic florencite group of phosphates and arsenates. Charge balance in eylettersite is maintained through partial occupancy of the Th site, and by substitution of Si forP. 

---