Silicate ores

Late rites, which are oxide/silicate ores such as gamierite, (Ni,Mg)6Si40io(OH)8, and nickeliferous limonite, (Fe,Ni)0 (0H).nH20, which have been concentrated by weathering in tropical rainbelt areas such as New Caledonia, Cuba and Queensland. 

The flotation of sulfidic, oxidic, and salt-type ores and, in special cases, silicate ores can be improved by the use of ether carboxylates as collectors [221,222]. In particular, the flotation of fluorite, barite, and scheelite is mentioned. Special synergistic combinations of ether carboxylates with fatty acids [223] and with vinyl- or alkylsulfonic acid polymer [224] are described. 

Hirabayashi (1907) defined Kuroko as an ore which is a fine compact mixture of sphalerite, galena, and barite. This definition can be applied to black ore , but not to yellow ore or siliceous ore because these minerals are not abundant in these ores. Kinoshita (1944) defined Kuroko deposit as a deposit genetically related to the Tertiary volcanic rocks, consisting of a combination of Kuroko (black ore), Oko (yellow ore), Keiko (siliceous ore), and/or Sekkoko (gypsum ore) (Matsukuma and Horikoshi, 1970). The deposit is generally defined as a strata-bound polymetallic sulfide-sulfate deposit genetically related to Miocene bimodal (felsic-basaltic) volcanism (T. Sato, 1974). 

Quartz is abundant in siliceous ore, barite ore and tetsusekiei ore. Minor amounts of Mg-minerals (talc, Mg-chlorite) occur in sekko ore. Chlorite occurs in. sekko ore and it contains high amounts of Mg (Fig. 1.18). 

Marutani and Takenouchi (1978) clarified the variations in homogenization temperature and salinity of inclusion fluids in quartz from stockwork siliceous orebodies at the Kosaka mine (Fig. 1.35 Urabe, 1978). They showed that the temperature decreases stratigraphically upwards from stockwork ore zone (280-320°C) to bedded ore zone (260-310°C). Pisutha-Arnond and Ohmoto (1983) carried out fluid inclusion studies of the stockwork siliceous ores from five Kuroko deposits (Kosaka, Fukazawa, Furutobe, Shakanai, and Matsumine) and revealed that black ore minerals (sphalerite, galena, barite) and yellow ore minerals (chalcopyrite, quartz) formed at 200-330°C and 330 50°C, respectively, and salinities of the ore fluids remained fairly constant at about 3.5-6 equivalent wt% NaCl. They analyzed fluids extracted from sulfides and quartz Na = 0.60 0.16 (mol/kg H2O), K = 0.08 0.05, Ca = 0.06 0.05, Mg = 0.013 0.008, Cl = 0.82 0.32, C (as CO2) = 0.20 0.15 and less than 6 ppm each for Cu, Pb, Zn and Fe. 

Figure 1.35. Summarized results of homogenization temperature determination in quartz from Uwamuki No. 4 Orebody shown for Kuroko-type (BSO) and Oko-type (YSO), and siliceous ores and for each level (Marutani and Takenouchi, 1978).

Sulfur isotopic data of separated pyrite as the commonest sulfide mineral (Kajiwara, 1971 Kajiwara and Date, 1971) show different values for the three sub-types of Horikoshi and Shikazono (1978). The values of pyrite in the C sub-type deposits are higher than the values of pyrite from the Y and B sub-types. The values of pyrite from the Y sub-type seem to be slightly higher than those from the B sub-type. Kajiwara and Date (1971) are of a different opinion the values from the Kosaka district are higher than those in the Hanaoka district, because all sulfur isotopic data from the C sub-type were obtained in the Kosaka district. The sulfur isotopic data on the obtained Uwamuki deposits of the B sub-type in the Hanaoka district indicate systematic decrease in 8 S passing from the yellow ore (4-7%o) to the black siliceous ore (4-5%c) (Bryndzia et al., 1983). Kajiwara and Date s data (1971) include three values of pyrite in the Doyashiki deposit of C sub-type in the Hanaoka district. The main Doyashiki... 

As noted already, Kuroko deposits are characterized by the following zonal arrangement in ascending stratigraphic order siliceous ore (quartz, chalcopyrite, pyrite), yellow ore (chalcopyrite, pyrite), black ore (sphalerite, galena, barite), barite ore (barite and quartz) and ferruginous chert ore (microcrystalline quartz, hematite). 

Quartz is abundant but barite is poor in the siliceous ore, though barite veinlets occur in this zone. 

Quartz occurs abundantly in feeder ore (stockwork siliceous ore) in Kuroko deposits. 

These predictions are generally in agreement with the observations homogenization temperatures of fluid inclusions in quartz from siliceous ore zone and in barite from black ore zone in the Kuroko deposits is relatively high, ranging from 350 to 250°C, and low, ranging from 250 to 150°C, respectively. 

A/M for the stockwork siliceous ore zone in Kuroko deposits is low, while that for black ore in the Kuroko deposits and chimney may be high. 

Barite is abundant and widespread in Kuroko deposits. However, it is concentrated especially in the upper horizons (black ore and barite ore), increasing upwards within the black ore. Such a trend is also observed frequently in the tetsusekiei, but rarely in the yellow ore. Barite occurs also as vein-fillings in the stockwork siliceous ore. 

Bryndzia, L.T., Scott, S.D. and Farr, J.E. (1983) Mineralogy, geochemistry, and mineral chemistry of siliceous ore and altered footwall rocks in the Uwamuki 2 and 4 deposits, Kosaka mine, Hokuroku district, Japan. Econ. GeoL Mon., 5, 507-522. 

Marutani, M. and Takenouchi, S. (1978) Fluid inclusion study of stockwork siliceous ore bodies of Kuroko deposits at the Kosaka mine, Akita, Japan. Mining Geology, 28, 349-360. 

Yamada, R., Suyama, T. and Ogushi, N. (1987) Gold-bearing siliceous ore of the Nurukawa Kuroko deposits, Akita prefecture, Japan. Mining Geology, 37, 109-118 (in Japanese with English abst.). 

Besshi-type deposits in Sanbagawa metamorphic terrain occur in the Minawa Formation which is composed of basic schist. Sometimes, they are associated with quartz schists. Probably, quartz has been originally formed from hydrothermal solution like siliceous ore in Kuroko deposits. Original rocks of basic schists are basaltic lava and hyaloclastics. Detailed geochemical investigation on the basic schists in the Sanbagawa... 

Another silicate ore treated by fluoridizing roasting is zircon. The ore is mixed with potassium hexafluorosilicate (K2SiF6) and heated in a rotary kiln at 650 to 700 °C to effect the reaction ... 

Saha, A. K. Khan, Z. H. Akerkar, D. D. Extraction of nickel from Indian low-grade siliceous ore. Trans. Inst. Min. Metall. Sect. C-Miner. Process. Extr. Metall. 1992, 101, C52-C56. 

Zinc is a bluish-white, lustrous metal which tarnishes in air. It is present in the earth s crust as sulfide (sphalerite), carbonate, or silicate ores, to the extent of only 78 ppm, making it the 23rd most abundant element.2 The metal is obtained from its ores by roasting and subsequent reduction with coke or by electrolysis. Approximately 8.36 million metric tons of zinc were produced worldwide in 2002 of this amount, two-thirds were from ores, while one-third was obtained from recycled zinc.3 The ease of mining and refining of the ore and the subsequent low price of the metal (ca. 1.2 kg-1 in 1998)3 have made zinc the third most popular non-ferrous metal (after aluminum and copper). 

The gangue constituents and their nature are sometimes determining factors in selection of a treatment process for beneficiation of oxide copper ores. Highly weathered ores usually contain a fairly large amount of slimes, which has a negative effect on the floatability of oxide copper minerals. Also, there is an appreciable difference in floatability between oxide minerals from carbonaceous and siliceous ores. 

Carboxilic acid flotation of malachite has been commercially used for over 70 years. This collector is prepared by heating a mixture of hydrolysed palm oil (or oleic acid) and fuel oil in a 3 1 ratio. This mixture is manly used for recovery of malachite from siliceous ores. The use of carboxylic acid for malachite flotation from carbonaceous ores resulted in both reduced concentrate grade and recovery. 

This mixture is passed through a colloidal mill in the presence of 0.5% soda ash solution. The fatty acid prepared in this manner does not produce voluminous froth and is more selective than ordinary fatty acid mixtures. Experimental laboratory testwork conducted on the Kolwezi siliceous ore [18] with the above-mentioned mixture, with different degrees of dispersion showed substantial differences in metallurgical results (Table 19.4). Poor results were achieved when there was no dispersion of the mixture. The best results were obtained when the mixture was treated for 10 min in an ultrasonic mixer. In each case, the mixture was dissolved in a 0.5% soda ash solution. 

For many years this plant has treated an oxide siliceous ore using the hydrolysed palm oil mixture. The palm oil-fuel oil mixture is heated to about 60°C in the presence of soda ash and then passed through a colloidal mill before it is added to the copper conditioner. A typical reagent scheme used to treat the Kolwezi siliceous ore is shown in Table 19.7. The soda ash and sodium silicate are added to the grinding mills and the palm oil emulsion to the copper conditioner. 

One of the main problems associated with beneficiation of the Kolwezi siliceous ore is the production of malachite and pseudomalachte slimes that have a relatively low flotation rate. Most of the copper losses occurring in the plant are in the -15 pm fraction. Experimental testwork conducted with a different palm oil emulsifier indicated that copper recovery from the fine fraction can be significantly improved with the use of petroleum sulphonate (Petrosol 845) as the emulsifier [21] for palm oil. Significant improvement in copper recovery was realized in the fine fractions with the use of palm oil emulsified with Petrosol 845. 

Reagent scheme used to treat the Kolwezi siliceous ore... 

Other plants that treat siliceous copper oxide ores include Panda and Kabolela plants from the same area. The gangue in this ore is composed of argillaceous and siliceous schist. Both plants essentially use the same flowsheet and reagent scheme, as that described for the Kolwezi plant. Typical plant results during treatment of a siliceous ore are presented in Table 19.8. These are average results achieved from 1980 to 1982. 

Occurrence. Important commercial ores of Ni are sulphides (such as pentlandite (Ni,Fe)9Sg) generally associated with Cu, Co and precious metals and oxide/silicate ores (as (Ni,Mg)6Si40io(OH)8 and (Fe,Ni)0(0H)nH20). It is also found in combination with As and Sb (as NiAs or in deposits consisting ofNiSb, NiAs2, etc.). It is also present as Fe alloys in several meteorites and probably in the core of the earth. 

Other substances— for example, the silicate ores, the carbonate ores, the titanium minerals— may be similarly grouped for pmposes of experi-piental study, but it is hardly necessary here to make a complete inventory of such groups. 

The lateritic hydrous nickel silicate ores are formed by the weathering of rocks rich in iron and magnesium in humid tropical areas. The repeated processes of dissolution and precipitation lead to a uniform dispersal of the nickel that is not amenable to concentration by physical means therefore, these ores are concentrated by chemical means such as leaching. Fateritic ores are less well defined than sulfide ores. The nickel content of lateritic ores is similar to that of sulfide ore and typically ranges from 1% to 3% nickel. Important lateritic deposits of nickel are located in Cuba, New Caledonia, Indonesia, Guatemala, the Dominican Republic, the Philippines, and Brazil. Fossil nickeliferous laterite... 

According to Ludwig Darmstaedter, the German copper deposits in the Harz were worked as early as the year 968 A.D. In 1450 Nessler, a metallurgist of Joachimsthal, showed that siliceous ores could be worked by roasting them, leaching out the copper vitriol with water, and depositing the copper from this solution on iron (158). 

Silicate ores can be solubilized by fusion with sodium carbonate. A simplified equation for what occurs is... 

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