Chert

Cherts CHESS Chevrefeuille Chevrel phase Chevron-Gulf process Chevron process... 

Sihceous matter other than clay may occur in the free state as sand, quartz fragments, and chert, and in the combined state as feldspar, mica, talc (qv), and serpentine. Metallurgical and chemical limestones should contain less than 1% alumina and 2% siUca. 

Mercury ore deposits occur in faulted and fractured rocks, such as limestone, calcareous shales, sandstones, serpentine, chert, andesite, basalt, and rhyolite. Deposits are mostiy epithermal in character, ie, minerals were deposited by rising warm solutions at comparatively shallow depths from 1—1000 m (6). 

The western phosphates are sedimentary deposits in adjoining areas of Wyoming, Idaho, and Utah derived from a former inland sea. They consist of layers of limestone, phosphate, and chert, now budded and faulted so they are rarely horizontal. The phosphate ore is strip-mined using large earth-moving equipment such as shovels, scrappers, dump tmcks, and bulldozers to mine the overburden and phosphate ore. Mining ratios of overburden to metric ton of recovered ore are from 1—3 m /1 (2—4 yd /short ton). The typical mining practice is to remove ore and overburden from a pit in discrete layers (Lifts) of 10—20 m in depth. Overburden from the pit is back-hauled to a previously mined pit. Extensive land reclamation practices are later carried out to return the mine areas to natural states. 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

Po22olans iaclude natural materials such as diatomaceous earths (see Diatomite), opaline cherts, and shales, tuffs, and volcanic ashes or pumicites, and calciaed materials such as some clays and shales. By-products such as fly ashes and siUca fume are also employed. In the United States the proportion of po22olan iaterground with clinker has varied from 15 to over 30%, whereas ia Italy, cements with a 30—40% po22olan content are produced. 

A microcrystalline impure form of silica similar to chert. Used for decorative purposes. Rare in industry. 

Nieckf. M. NiEGERandfv Rfachert Angeu-. Chert./nr. Edn. Engl. 27. 1715-6 (1988). 

Schimtnel, the nmoum of tlii.-. c tc-i present is aLiout lU per cent., aner cent, of the Iree alcohol lu chi- oil. There is also present a small amount ol either au aldehvdc or a kclone boiling liccwecu JJO and tioCr, yielding a hydraaoDO meliiug at 4 F and an oxime melting ai So". 

Berg-kalk, m. rock time (Geol.) mountain limestone. -kiesel, m. rock flint, chert felsite. -kohle,/. (mineral) coal, -kork, m. mountain cork (a light form of asbestos), -kreide, /. rock lime, -kristall, -krystall, m. rock crystal (transparent quartz), -kupfer, n. native copper, -lasur, /. azurite. -leder, n. mountain leather (a form of asbestos), -maun, m miner. 

The companion of insert bits cutting structure is shown in Figure 4-142 [44]. Initially, the tungsten carbide tooth bit was developed to drill extremely hard, abrasive cherts and quartzites that had been very costly to drill because of the... 

Select a tungsten carbide insert bit with no offset and conical or double cone inserts when drilling hard and abrasive limestone, hard dolomite, chert, pyrite, quartz, basalt, etc. Use bit type 7-4 to 8-3. 

CHERT Hwd-laoed spiral forhaidlor-mabonewhkhmuti be removed by crueMng. Cutters are lur-niahed tNih indusirial chrome-plated pine. 

A porous siliceous rock resulting from the decomposition of chert or siliceous limestone. Used as a base in soap and scouring powders, in metal polishing, as a filtering agent, and in wood and paint fillers. A cryptocrystalline form of free silica. 

In the Chichibu Zone, the intimate association of abundant strata-bound Mn-Fe deposits, limestone-dolomite and silica (chert) with basic volcanic rocks suggests an ocean-ridge hydrothermal origin. 

Figure 1.2. Distribution of the stratiform Cu-sulfide and chert-hosted Mn deposits in Japan (Sato and Ka.se, 1996). MTL Median Tectonic Line TTL Tanakura Tcetonic Line ISTL Itoigawa-Shizuoka Tectonic Line BTL Butsuzo Tectonic Line.

The lowest rock units are basement rocks, composed of phyllites, cherts, and minor sandstone probably of Paleozoic age. The oldest Tertiary formation, which is called Ohya... 

Positive Eu anomaly is observed for barite, Kuroko ores, ferruginous chert (tet-susekiei), and hydrothermally altered basaltic and dacitic rocks overlying the Kuroko ores. 

Figure 1.46. REE patterns of the altered volcanogenic rocks and Kuroko ores. Data sources Shikazono (1999a). (A) Hydrothermally altered dacite and anhydrite underlying the Kuroko ores. (B) Barite, Kuroko ore and ferruginous chert. (C) Hydrothermally altered basalt overlying the Kuroko ores (Shikazono, 1999a).

Light rare earth enrichment is distinct and REE contents are relatively high for the ferruginous chert. 

Heavy Rare Earth Element). Therefore, it is considered that negative Ce and positive Eu anomalies in hydrothermally altered volcanic rocks, Kuroko ores, and ferruginous chert and LREE enrichment in the Kuroko ores have been caused by hydrothermal alteration and precipitations of minerals from hydrothermal solution responsible for sulfides-sulfate (barite) mineralization. 

Positive Eu anomaly is observed for hydrothermal solution issuing from the hydrothermal vent on the seawater at East Pacific Rise (Bence, 1983 Michard et al., 1983 Michard and AlbarMe, 1986). Guichard et al. (1979) have shown that the continental hydrothermal barites have a positive Eu anomaly, indicating a relatively reduced environment. Graf (1977) has shown that massive sulfide deposits and associated rocks from the Bathurst-Newcastle district. New Brunswick have positive Eu anomalies. These data are compatible with positive Eu anomaly of altered basaltic rocks, ferruginous chert and Kuroko ores in Kuroko mine area having positive Eu anomaly and strongly support that Eu is present as divalent state in hydrothermal solution responsible for the hydrothermal alteration and Kuroko mineralization. 

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). 

Barite is common in the black ore and abundant in barite ore. Barite is also found in ferruginous chert ore (Kalogeropoulos and Scott, 1983). 

Ferruginous chert in which abundant silica occurs formed below the seafloor by the mixing of ferruginous sediments and hydrothermal components (Kalogeropourous and Scott, 1983). 

Barite-silica chimney found in back-arc basin formed in the conditions similar to that of ferruginous chert and barite bed in the Kuroko deposits temperature is relatively low (ca. 150-100°C), and flow rate of fluids may be slow. 

Barite is abundant in the massive strata-bound ore bodies (black and barite ores) in Kuroko deposits and occurs in the ferruginous chert ore in Kuroko deposits, and chimneys in active deposits at back-arc basins. 

Geology of the province is composed of Paleozoic basements. Tertiary altered submarine volcanic and sedimentary rocks (Green tuff) and Quaternary volcanic rocks. The basements are shale, tuff, limestone and chert of unknown ages. A simplified geologic map is shown in Fig. 1.148. 

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