Shale mineral composition

Schist is a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye. It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity.

Siltstone is a sedimentary rock composed mainly of silt-sized particles. It forms where water, wind, or ice deposit silt, and the silt is then compacted and cemented into a rock. Silt accumulates in sedimentary basins throughout the world. It represents a level of current, wave, or wind energy between where sand and mud accumulate.Oil shale is a type of sedimentary rock that is rich in kerogen. Kerogen is a part of rock that breaks down and releases hydrocarbons when heated. Hydrocarbons are substances made entirely of hydrogen and carbon. Petroleum and natural gas are probably the most familiar . hydrocarbons.The hydrocarbons in oil shale can be used as an …Shale is an important mineral resource in Ohio and has the same uses as clay. Shale used in Ohio is from Devonian and Carboniferous (Mississippian and Pennsylvanian) rocks. Composition: Various clay minerals with small amounts of other compounds. Additional Information. Annual Report on Ohio's Mineral Industries.Jan 31, 2019 · Shale gas content and composition characteristics. The shale gas content of the Longmaxi Formation in the CK-1 well is high, ranging from 0.07 m 3 /t to 1.52 m 3 /t, with an average value of 0.60 ... Limestone Rhyolite Slate Shale. rhyolite. Compaction is most significant as a lithification process for sedimentary rocks composed of sand-sized particles. ... Produces smaller pieces Adds to the effectiveness of chemical weathering Does not change the rock's mineral composition Does not affect metamorphic rocks. Does not affect metamorphic ...Slate was formed under low-grade metamorphic conditions— i.e., under relatively low temperature and pressure. The original material was a fine clay, sometimes with sand or volcanic dust, usually in the form of a sedimentary rock ( e.g., a mudstone or shale). The parent rock may be only partially altered so that some of the original mineralogy ...

১ জুল, ২০২২ ... The results of X-ray diffraction, thermogravimetric and FTIR spectroscopy analyses of mineral composition in- dicated that the El-Lajjun oil ...To study the influence of different organic-inorganic composition on the adsorption in shale, taking the Niutitang Formation shale in the Huijunba syncline in southern Hanzhong as the research object, based on acid treatment to extract kerogen and wet chemicals. Extracting mineral components by oxidation method, a series of isothermal adsorption experiments were carried out on the original ...The mineral composition of shale is closely related to its elements and their relations vary with lithology. Taking the Wufeng-Longmaxi marine shale from well XK01 as an example, after obtaining the elemental data of shale cores in situ by a portable XRF analyzer and testing the mineral compositions of identical cores by XRD apparatus in the ...Schist is a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye. It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity. Nov 18, 2021 · The mineral composition of the shale in the Ek 2 is mainly felsic minerals (quartz and feldspar), carbonate minerals (calcite and dolomite), clay minerals, and other minerals such as analcime and pyrite. The content of felsic minerals is mostly concentrated in 20–44%, with an average of 32.82%; the content of carbonate minerals is mostly ...

Using XRD, low-temperature N 2 adsorption, and porosity measurements, the changes in mineral composition and pore structure characteristics of shale samples were measured. The conclusions of this ...The brittleness of shale is determined by its mineral composition, minerals such as quartz, dolomite, feldspar, mica et al. are used to evaluate the brittleness of shale (Jarvie, 2007). Due to the dynamic change of the shales physical properties, brittleness is not an inherent property of the shale.Ten shale samples from the first member of Qingshankou Formation in the Songliao Basin are measured using XRD, the composition of the whole shale and clay minerals are shown in Figure 1; the fluid ... By mineral composition classification, the mineral composition of tailings can be divided into clay minerals, non-clay minerals, and metal minerals. The mineral contents of the tailings are listed ...The mineral composition of shale largely determines the hydrocarbon generation capacity and the fracturing design in shale gas reservoirs (Zhang et al., 2011, 2019). The mineral composition of source rocks is an important index for judging whether high-quality source rocks can form shale gas reservoirs with economic values ( Bowker …The mineral composition of shale largely determines the hydrocarbon generation capacity and the fracturing design in shale gas reservoirs (Zhang et al., 2011, 2019). The mineral composition of source rocks is an important index for judging whether high-quality source rocks can form shale gas reservoirs with economic values ( Bowker …

Chemical formula for sphalerite.

The alkaline lacustrine shale of FF presents a complex mineral composition, which primarily consists of quartz, feldspar, dolomite, calcite, pyrite, etc.; …Schist is a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye. It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity. 2.1 Artificial Core Production 2.1.1 Material Selection. To study the effects of the ratio of brittle and clay mineral particle sizes on shale porosity and permeability, the shale mineral particle size must be on the order of a micrometer, as in the Longmaxi Formation shale (Li et al. 2016a; Zhu et al. 2018).The quartz powders and smectite …7.5.1: Clastic Sedimentary Rocks. Page ID. Dexter Perkins. University of North Dakota. Clastic sedimentary rocks are formed by compaction and cementation of clasts composed of individual mineral grains or pieces of rock. Because their mineralogy varies so much, we generally classify clastic rocks based on grain size rather than …Sandstone can contain a variety of mineral grains, including quartz, feldspar, lithic fragments, and sometimes mica or clay minerals. Shale: Shale is a sedimentary rock composed primarily of clay minerals, such as kaolinite, illite, and/or montmorillonite. Shale may also contain other minerals like quartz, feldspar, and calcite.In this regard, the complex processing of black shale ore based on a detailed study of its mineral composition for the extraction of rare and REEs is a critical scientific and technical issue. The first extraction of valuable elements from the ore of the Balasauskandyk deposit was performed in the mid-twentieth century ( Ankinovich and ...

Description. Shale is a sedimentary rock composed of very fine clay particles. Clay forms from the decomposition of the mineral feldspar. Other minerals present in shale are quartz, mica, pyrite, and organic matter. …In 2013, when studying the Lower Cambrian, Upper Ordovician Lower Silurian, and Upper Permian shale of Southern Paleozoic, Chen and Xiao noted that the mineral composition of Southern Paleozoic shale is relatively complex, and the brittleness index calculation has gradually developed from unclear qualitative analysis to accurate quantitative ...The rock composition and grain size determine the compressive, tensile, and shear strength of shale, which affects the degree of shale fracture under stress. One of the most significant factors influencing fracture development is the mineral composition and content of organic-rich shale [22], manifested in the following two aspects. (1) Black ...Intrusive (or, plutonic) igneous rocks form from magma that has cooled below the Earth's surface. Because this cooling process is slow, visible (or, phaneritic) mineral grains have time to form and are usually visible with the naked eye. When any mineral grains in a sample exceed 2 cm in size, the rock is called a pegmatite.Description. Shale is a sedimentary rock composed of very fine clay particles. Clay forms from the decomposition of the mineral feldspar. Other minerals present in shale are quartz, mica, pyrite, and organic matter. …On this basis, the influencing factors of the oil retention are summarized from the microscale to the macroscale. The oil retention capacity is comprehensively controlled by organic matter abundance, type and maturity, mineral composition and diagenesis, oil storage space, shale thickness, and preservation conditions. Nov 28, 2022 · Rock Composition. Slate consists of clay minerals (micas) depending on the exposure level of metamorphism during the formation process. The clay minerals in shale or mudstone change to micas with increasing levels of heat and pressure. The more heat and pressure it receives, the more aligned and crystallized the rocks become. internal standard and the dozen or so minerals in the Pierre Shale. Clinoptilolite is used as defined by Mumpton (1960) because in the Pierre Shale this mineral is stable when heated at 550°0 for half an hour. Peak intensities for the different varieties of feldspar vary with the chemical composition of the feldspar. Aug 17, 2022 · Brittle minerals in the mineral composition, such as quartz, feldspar, and calcite, are the main internal factors controlling the degree of fracture development, and directly affect the storage space and seepage channels of shale (Chen et al., 2012). Although pyrite is a brittle mineral, its content is generally low, and its contribution to the ... Shale is a sedimentary rock composed of fine-grained sediment, such as clay minerals. Schist is a medium-grade metamorphic rock, which slate can be metamorphosed to if it is exposed to enough heat ... Three minerals were mapped in the Eagle Ford rock sample, for which there were 8 elements characterized. In the testing phase, the minerals were correctly classified with accuracy of 97 % and ... In 2013, when studying the Lower Cambrian, Upper Ordovician Lower Silurian, and Upper Permian shale of Southern Paleozoic, Chen and Xiao noted that the mineral composition of Southern Paleozoic shale is relatively complex, and the brittleness index calculation has gradually developed from unclear qualitative analysis to accurate quantitative ...

Three minerals were mapped in the Eagle Ford rock sample, for which there were 8 elements characterized. In the testing phase, the minerals were correctly classified with accuracy of 97 % and ...

2.3. Comprehensive evaluation method. Estimating shale brittleness by rock mechanics or brittle minerals is not sufficient. On the one hand, people often ignore the differences in the chemical composition, mechanical properties, and brittleness of various brittle minerals; researchers suppose that each mineral has the same contribution to …The mineral compositions (measured by XRD with a Bruker-AXS D9 Advance Diffract Meter) are presented in Fig. 5 (for the (seven) silty laminae shale samples and the (eleven) argillaceous shale samples). The major minerals in lacustrine shales are: clay minerals, quartz, anorthose (NaAlSi 3 O 8 –CaAl 2 Si 2 O 8), buddingtonite (NH 4 AlSi 3 O 8 ...Phyllite is a foliated metamorphic rock that has been subjected to low levels of heat, pressure and chemical activity. It is composed mainly of flake-shaped mica minerals in parallel alignment. The strong parallel alignment of the mica grains allows the rock to be easily split into sheets or slabs. The alignment of the mica grains gives ... Oil shale semi-coke (OSSC) is a typical industrial waste derived from oil shale after distillation of oil shale, and it is composed of multi-minerals (kaolinite, illite, quartz, feldspar, etc.) and organic matters (Huang et al. 2019; Raukas and Punning 2009; Yörük et al. 2018), in which organic matters are tightly bound to minerals each other ...By mineral composition classification, the mineral composition of tailings can be divided into clay minerals, non-clay minerals, and metal minerals. The mineral contents of the tailings are listed ...Mar 21, 2023 · Shale oil reservoirs are characterized by complex lithology, complex mineral composition and strong heterogeneity. This causes great difficulty in lithologic evaluation. In this paper, a method of lithology identification is proposed by means of intersection plot method and machine learning method, and lithology evaluation is carried out by combining the calculation of mineral content with a ... Natural gas hydrate is a kind of environmentally friendly unconventional energy with large reserves, which attract increasing attention in recent years. The microscopic pore structure and mineral composition of natural gas hydrate reservoir have a great influence on its seepage characteristics during exploitation. In this study, computed tomography and scanning electron microscope are used to ...Composition of Shale. Shale is a rock composed mainly of clay-size mineral grains. These tiny grains are usually clay minerals such as illite, kaolinite, and smectite. Shale …Natural gas hydrate is a kind of environmentally friendly unconventional energy with large reserves, which attract increasing attention in recent years. The microscopic pore structure and mineral composition of natural gas hydrate reservoir have a great influence on its seepage characteristics during exploitation. In this study, computed tomography and scanning electron microscope are used to ...The shale samples, however, are classified as siliceous shale, calcareous shale and mixed shale as shown in the mineral composition ternary diagram (Fig. 2, Fig. 7 b). The clustered data distribution indicates the similarity in mineral composition and difference in TOC values for the first and third members of the Shahejie Formation.

Sumner craigslist.

E u countries map.

The specific type of schist formed depends on factors like the mineral composition of the protolith and the conditions of temperature and pressure during metamorphism. Metamorphic Grade and Index Minerals: Schist is associated with intermediate to high metamorphic grades. Metamorphic grade refers to the intensity of metamorphism a rock has ...Wood is not a mineral. A mineral is a naturally occurring inorganic solid with a definite chemical composition and an ordered internal structure. Although wood is a naturally occurring solid, it is an organic material, so it is not a minera...The mineral composition is complex, with siliciclastic minerals, carbonate minerals, and clay minerals accounting for the absolute majority of the total mineral content, but other mineral types, such as sulfate minerals, halides, or zeolites are also commonly present [16,17,18]. Precisely because of the heterogeneity of lacustrine shale, it ...In this regard, the complex processing of black shale ore based on a detailed study of its mineral composition for the extraction of rare and REEs is a critical scientific and technical issue. The first extraction of valuable elements from the ore of the Balasauskandyk deposit was performed in the mid-twentieth century ( Ankinovich and ...Composite wood decking is becoming increasingly popular as a material for outdoor decks. It is durable, low maintenance, and comes in a variety of colors and textures. With its versatility and range of colors, composite wood decking can be ...Music is a universal language that has the power to move and inspire people. Whether you’re an aspiring musician or simply someone who enjoys listening to music, there’s something magical about creating your own compositions.Type Metamorphic Rock Texture Foliated; Very fine-grained Composition Chlorite, Plagioclase, Quartz Index Minerals Color Bluish-gray Miscellaneous Foliation surface is dull and planar; Slaty Cleavage Metamorphic Type Regional Metamorphic Grade Low Grade (Low P – Low T) Parent Rock Shale or Mudstone Metamorphic Environment Low grade …XRD analysis of shale samples from well L-2 (Figure 2a) and other seven wells (Figure 2b) in the Long-1 1 sub-section in the southern Sichuan Basin indicates that the mineral composition of the shales in the study area is diverse, mainly quartz, followed by clay minerals, and also including carbonate minerals such as feldspar, calcite, and ...Classification based on Mineral Composition: ... The original parent rock (or protolith) of mica schist is shale. Phyllite could also be considered the parent rock as mica schist is a more highly metamorphosed phyllite. References. Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing. ...Typical mineral composition of Marcellus Shale is 10%–60% of quartz, 10%–35% of clay minerals primarily with illite, 3%–50% of calcite, dolomite, and siderite, 0%–4% of feldspars, 5%–13% of pyrite, 5%–30% of mica, and trace of phosphate and gypsum (NETL, 2011). Both Marcellus and Barnett plays show significant success because of ...Limestone (calcium carbonate CaCO 3) is a type of carbonate sedimentary rock which is the main source of the material lime.It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO 3.Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place … ….

Shale is a type of sedimentary rock that forms in muddy, clay mineral-filled environments. Like all sedimentary rock, it forms from the weathering by-products of other rocks, usually those ...Rock Composition. Shale and other mudstones are primarily composed of clay minerals. The major clay minerals include kaolinite, illite, and montmorillonite. A typical shale is made of clay …Hence, shale tends to be weak, requiring support for bearing loads. In addition, depending upon the type of clay minerals present, shale may present shrink/swell problems (smectite and chlorite minerals), or squeeze/deformation problems (kaolinite and chlorite minerals). Siltstone Key Point. Silt does not have a precise composition.Nov 1, 2022 · 2.3. Comprehensive evaluation method. Estimating shale brittleness by rock mechanics or brittle minerals is not sufficient. On the one hand, people often ignore the differences in the chemical composition, mechanical properties, and brittleness of various brittle minerals; researchers suppose that each mineral has the same contribution to rock brittleness (except for difference in the contents). The mineral compositions (measured by XRD with a Bruker-AXS D9 Advance Diffract Meter) are presented in Fig. 5 (for the (seven) silty laminae shale samples and the (eleven) argillaceous shale samples). The major minerals in lacustrine shales are: clay minerals, quartz, anorthose (NaAlSi 3 O 8 –CaAl 2 Si 2 O 8), buddingtonite (NH 4 AlSi 3 O 8 ...Aug 30, 2022 · Relationship between the fractal dimension and shale mineral composition There are many types of organic shale minerals, including quartz, feldspar, calcite, dolomite, clay minerals, pyrite, etc. There are certain differences in the content of mineral components in different regions, and their effects on the fractal dimension are also different ... Shale, any of a group of fine-grained, laminated sedimentary rocks consisting of silt- and clay-sized particles. Shale is the most …Mar 16, 2023 · Based on thin-section observation and mineral composition, a total of 10 representative shale samples with different mineralogy and textures were cautiously selected for field-emission scanning electron microscopy (FE-SEM) analysis to observe the arrangement and distribution of different minerals, OM, various pores, and microfractures. Relatively porous and soft, shale is able to readily take up and release minerals ... Thus, the composition of shales is quite various, heavily depending on the ... Shale mineral composition, The Acid Test on Rocks. LIMESTONE, DOLOSTONE, AND MARBLE. Some rocks contain carbonate minerals, and the acid test can be used to help identify them. Limestone is composed almost entirely of calcite and will produce a vigorous fizz with a drop of hydrochloric acid. Dolostone is a rock composed of almost entirely of dolomite. It will …, Abstract. Quantitative X-ray diffraction analysis gives data on quartz, feldspar, and carbonate in shales with a precision of + or -10 percent; clay mineral content is determined by difference. Obviously silty and calcareous shales were not included among the 400 samples from Tertiary rocks of the Gulf Coast, Mesozoic rocks from the western ..., The test results showed that during hydraulic fracturing, the original mineral composition of the shale may impact the pore structure and hence shale gas recovery. Therefore, the fracturing fluid ..., Therefore, mineral composition is of great significance to the evaluation and exploration and development of shale gas reservoirs. Taking the Paleogene shale …, The establishment of shale models that can accurately describe the composition and structure of shale is essential to perform molecular simulations of gas adsorption in shale reservoirs. This Review provides an overview of shale models, which include organic matter models, inorganic mineral models, and composite shale models., Once the fracturing water is absorbed into the shale matrix, the clay minerals will experience swelling, shrinkage and hydration damage. ... The mineral composition was measured by using the XRD ..., have a similar mineral composition are not similar in either texture or mineral composition are similar in both texture and mineral composit. ... shale chert none of these. granite. Select from the list below the coarse-grained rock which is composed mainly of quartz and potassium feldspar. basalt andesite granite, Andesite is the name of a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. They have a mineral composition that is intermediate between granite and basalt. Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates., In terms of origin, most shale rock's constituent minerals are either: allogenic – clasts of rocks and minerals are brought into sedimentary basins, in which the shales are formed, …, Jun 1, 2021 · The rock composition and grain size determine the compressive, tensile, and shear strength of shale, which affects the degree of shale fracture under stress. One of the most significant factors influencing fracture development is the mineral composition and content of organic-rich shale [22], manifested in the following two aspects. (1) Black ... , Black shale is a dark-colored mudrock containing organic matter that may have generated hydrocarbons in the subsurface or that may yield hydrocarbons by pyrolysis. Many black shale units are enriched in metals severalfold above expected amounts in ordinary shale. Some black shale units have served as host rocks for syngenetic metal deposits.Black …, Jun 14, 2022 · In addition, heterogeneity is an inherent attribute of shale reservoirs, which is manifested in sedimentary facies and lithofacies at the macrolevel and mineral composition, organic geochemical ... , Slate is a fine-grained, metamorphic rock formed by compression of sedimentary shale, mudstone, or basalt. Gray slate is common, but the rock occurs in a variety of colors, including brown, purple, green, and blue. Slate consists mainly of silicates (silicon and oxygen), phyllosilicates (potassium and aluminum silicate), and aluminosilicates ..., Apr 1, 2023 · Mineralogy-based brittleness index is the simplest and most widely used index in characterizing the brittle property of shale gas/oil reservoirs. Traditionally, mineral compositions are usually determined by laboratory X-ray diffraction (XRD) analysis or interpreted from element logging, among which the former is time-consuming and non-continuous while the latter is costly and not timely. In ... , The shales from Es 4upper are the favorable interval for shale oil accumulation and flow, especially for the shales with depth ranges of 3360∼3410 m, which possess high …, In this study, the mineral composition of shale samples was analyzed. The samples were scanned using a SEM, and mineral analysis was done by X-ray diffraction for semi-quantitative analysis of the core phase. Detailed information of the mineral composition content and each element content is given in Table 2. Generally speaking, quartz, albite ..., The alkaline lacustrine shale of FF presents a complex mineral composition, which primarily consists of quartz, feldspar, dolomite, calcite, pyrite, etc.; …, The average shale comprises 59 per cent. clay minerals, 20 per cent. quartz and chert, 8 per cent. felspars, 7 per cent. carbonates, 3 per cent. iron oxide minerals, 1 per cent. organic matter and 2 per cent. other minerals. Illite predominates among the clay minerals. , The specific type of schist formed depends on factors like the mineral composition of the protolith and the conditions of temperature and pressure during metamorphism. Metamorphic Grade and Index Minerals: Schist is associated with intermediate to high metamorphic grades. Metamorphic grade refers to the intensity of metamorphism a rock has ..., Oil shale, any sedimentary rock containing various amounts of solid organic material that yields petroleum products, along with a variety of solid by-products, when subjected to …, Composite wood decking is becoming increasingly popular as a material for outdoor decks. It is durable, low maintenance, and comes in a variety of colors and textures. With its versatility and range of colors, composite wood decking can be ..., As a clean energy, shale gas has become one of the hot fields in global oil and gas research (Chen et al., 2011; Gross et al., 2015).In recent years, China's shale gas production has been growing rapidly, and national shale gas demonstration areas such as Fuling, Changning, Weiyuan and Zhaotong have been built (Dong et al., 2016).In 2020, …, Sedimentary rocks are classified there rather simplistically according to physical characteristics and composition into detrital and nondetrital rocks. Numerous other attempts have Sedimentary rock - Classification, Deposits, Types: In general, geologists have attempted to classify sedimentary rocks on a natural basis, but some schemes have ..., The mineral species and composition ratios in coal samples are presented in Table 2. It was more reasonable to analyze the mineral composition by mineral groups, because of the different classes of mineral species observed in coal. These minerals are mainly clay minerals and to a lesser extent carbonates, sulfides, sulfates, and quartz., Recent studies have shown that shale has strong heterogeneity in mineral composition, structure, and pore structure [40–48]. The lighter layers contain more quartz and less clay minerals than the darker ones. Changes in mineralogical composition from microscopic FTIR spectra along the length of the sample are clearly shown (Figure 5). Color ..., Siltstone is a sedimentary rock composed mainly of silt-sized particles. It forms where water, wind, or ice deposit silt, and the silt is then compacted and cemented into a rock. Silt accumulates in sedimentary basins throughout the world. It represents a level of current, wave, or wind energy between where sand and mud accumulate., The different minerals in shale can be identified by EDS mapping, since each mineral has a particular chemical or elemental composition. For example, quartz is composed of silicon and oxygen atoms, the characteristic elements of carbonate are calcium and magnesium, while clay minerals are hydrous aluminium phyllosilicates [ 48 ]., Shale: Exhibits lamination or fissility. Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one ..., Outcrop of Ordovician kukersite oil shale, northern Estonia Lower Jurassic oil shale near Holzmaden, Germany. Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale …, Jul 1, 2021 · The mineral composition of shale largely determines the hydrocarbon generation capacity and the fracturing design in shale gas reservoirs (Zhang et al., 2011, 2019). The mineral composition of source rocks is an important index for judging whether high-quality source rocks can form shale gas reservoirs with economic values ( Bowker et al., 2007 ). , Apr 10, 2020 · Therefore, mineral composition is of great significance to the evaluation and exploration and development of shale gas reservoirs. Taking the Paleogene shale reservoir in Liaozhong Sag as an ... , More accurately, fine-grained deposits with grain size less than 62.5 μm can be defined as shale, which has nothing to do with mineral composition and lithofacies (Jiang and Tang, 2017). The CY2 well in the SHG area in the Eastern Qaidam Basin exhibits good gas show from the Carboniferous Keluke transitional organic-rich shales ( Cao et al ..., A shale with at least 1% carbonaceous material indicating a reducing environment. A dark, thinly laminated carbonaceous shale, exceptionally rich in organic matter (5% or more carbon content) and sulfide (esp. iron sulfide, usually pyrite ), and often containing unusual concentrations of certain trace elements (U, V, Cu, Ni).