How to identify small obsidian fragments like sand grains? In most cases it is not too hard to do by optical examination only. Obsidian is usually black although reddish varieties are pretty common also. Obsidian has a strong luster and conchoidal fracture. This means that fracture surface is smoothly curving like a seashell. Obsidian is usually black. This color is caused by minute inclusions and tiny crystals in the glass. Red color is caused by the same stuff that gives red color to weathered basalt, desert sand and K-feldspar.
It is mineral hematite iron oxide. Obsidian is usually dark and its surface is shiny. Obsidian is not stable in the weathering environment but it does not mean that it can not last millions of years. Obsidian on the Moon may be billions of years old because the Moon is dry.
The same applies here on the Earth as well. In dry areas obsidian can last pretty long. However, obsidian formations older than the Cenozoic it began 65 million years ago are unknown. Obsidian from the Yellowstone National Park. Width of view 35 mm.
Width of view 22 mm. Does anyone know? I presume its because its glass but non of the websites say. This is the best website on obsedian I can find. I will just put that its shiny because its glass in my work, thanks for your help. These metal ions are of significant importance as they are not biodegradable and cannot be metabolized by the environment but tend to accumulate in living organisms, causing various diseases and disorders.
Also, they can only be diluted or transformed, not destroyed [ 22 ]. These heavy metal ions pose serious health implications to the vital organs of human beings and animals when consumed above certain threshold concentrations.
There are various techniques for the removal of these toxic metal ions such as chemical precipitation, solvent extraction, ion exchange, reverse osmosis, and nanofiltration.
Among these techniques, adsorption is considered effective and economic due to its high efficiency, low-cost possibilities, easy handling, and the availability of different adsorbents. In this sense, perlite is a material with high potential due to its low cost and high availability. Table 2 reports the adsorption capacity of perlite in various cations [ 19 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].
Several authors have established that the perlite can improve its adsorption capacity by a thermal treatment to expand the perlite structure, and then, this material has been coated by chitosan. Chemical interaction between chitosan and the cations in solution. Other authors have pointed that expanded perlite can host certain oxides, which adsorb certain cations with high selectivity. Perlite can also act as a barrier to isolate radioactive wastes [ 35 , 40 , 41 ]. Interaction of polyacrylamide and polyhydroxyethylmethacrylate with cations.
Thus, Vijaya et al. Dyes and pigments are highly used organic compounds as colorants in a wide variety of products. These processes generate wastes that are often released together with wastewater.
The treatment of these wastewaters is one of the main environmental issues since these residues are very dangerous for the environment and harmful to health. Wastewater from the textile industry is processed in biological treatment plants. These processes are not very efficient so it is necessary to use complementary or alternative processes to eliminate these organic compounds from the water. Several processes such as precipitation, flocculation, coagulation, ion exchange, reverse osmosis, ozonization or adsorption have emerged as processes to remedy these emissions of dyes and pigments.
Adsorption is one of the processes mostly used to remove organic compounds from wastewater. Active carbon is the adsorbent that has shown the greatest adsorption capacity; however, this adsorbent is synthesized from various physical and chemical processes, which raises the price of the process in comparison with the natural adsorbent that are inexpensive and highly available, although its adsorption capacity is lower.
Among these adsorbents, perlite is a low-cost material with great potential to adsorb pigments and dyes. Thus, several studies have been carried out for the adsorption of cationic dyes as methylene blue [ 20 ], methyl violet [ 45 , 46 ], C. Cationic dyes adsorbed onto perlite. In all cases, the adsorption process is favored under basic conditions since perlite negatively charged interacts with the dye positively charged as indicates the following reactions Anionic dyes adsorbed onto perlite.
The adsorption processes are favored under slightly acid conditions since the electrostatic interactions increase, as indicated in the following scheme.
Surfactants are among the most versatile of the products of the chemical industry, being used as detergent, in pharmaceuticals, in prospecting for petroleum. However, the application of surfactants can also produce environmental pollution and raises a series of problems for wastewater treatment plants. One of the characteristic features of surfactants is their tendency to adsorb at interfaces in an oriented fashion. Similarly to the dyes, the surfactants can be classified into cationic and anionic so the adsorbent-surfactant interactions should be similar; however, the long hydrocarbon chains give rise to a polar section and another nonpolar in the surfactant, so nonelectrostatic interactions appear.
Considering this premises, an inexpensive adsorbed as perlite has been used to adsorb a cationic surfactant such as cetyltrimethylammonium bromide CTAB , obtaining a maximum adsorption value of 0. As takes places in cationic dyes, the adsorption is favored in basic conditions since the negatively charged surface of the perlite interacts with the cationic surfactant.
Interaction between a cationic surfactant and perlite in basic conditions. In the same way, the adsorption capacity of the expanded perlite was evaluated in anionic surfactant using sodium dodecylbenzenesulfonate Figure 15 as target molecule [ 56 ], reaching an adsorption value of 0.
Chemical structure of sodium dodecylbenzenesulfonate. Pezzella et al. This process takes place by H-bond interactions. In addition, considering that perlite can also be used as lightweight aggregate concrete, this material has also been used to the adsorption of an antibiotic as cefixime [ 60 ] or even the immobilization of bacteria [ 61 ].
Phenolic compounds are generally considered to be one of the most important organic pollutants discharged into the environment causing serious damage to health, unpleasant taste and odor. The major sources of phenol pollution in the aquatic environment are wasterwaters from the paint, pesticide, coal conversion, polymeric resin, petroleum, and petrochemicals industries. Africa Udachnaya Russia. Komatiites Alexo Canada Belingwe Zimbawe. Ol Doinyo Lengai Natrocarbonatite lava.
Volcanic glass Volcanic glass is the amorphous uncrystallized product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the close-packed, highly ordered array of a crystal and the highly disordered array of gas.
Most rocks that are largely glass are rhyolite, however, interstitial basaltic glass is common in basalt flow. Ash grains in the coarse fraction have various appearances under a binocular microscope: opaque white-colored grains, opaque gray-colored grains, translucent brownish gray-colored grains, translucent white-colored grains, transparent grains, and free crystals Fig. The complete table of the mineral assemblages is included in the supplemental material Additional file 1.
Photographs of ash particles from the September 27, eruption. Partly altered volcanic fragments are common in the ash, occurring as angular to subangular blocky fragments of partly altered volcanic rocks and minerals comprised of plagioclase, orthopyroxene, and magnetite. The partly altered rock fragments preserve the texture of volcanic rocks containing volcanic glass.
Isolated crystals of plagioclase and orthopyroxene are inferred to be derived from volcanic rocks because they contain glass inclusions.
Volcanic rocks of the cone are the source of the minerals, which contain them as phenocrysts Yamada and Kobayashi Two types of groundmass-derived fragments were identified: one consisting of abundant volcanic glass and minor microlites of plagioclase and pyroxene that form hyalo-ophitic texture, and the other one consisting of microlites of plagioclase, anorthoclase, and sanidine, and minor interstitial glass that form hyalopilitic texture Fig. The original igneous minerals and glass are partly replaced by pyrite, silica mineral, kaolin-group mineral, and muscovite.
BEI images of volcanic ash particles. Some of plagioclase microlites and glass were replaced by pyrite, silica mineral, kaolin-group mineral, and muscovite. Pyroxene phenocryst is replaced by silica mineral, and pyrite crystals fill the cleavage of the pseudomorphs. Narrow veinlets of vug and pyrite crystals are recognized in the deformed part arrow. Original crystals were replaced by silica mineral or kaolin darker or became void.
The colloform texture consists of K-feldspar-rich bands brighter and a fine-grained mixture of silica mineral and K-feldspar darker. Anhydrite crystals bright are attached conjugate with the grain. This association consists dominantly of silica mineral, subordinate pyrite, and minor rutile. Grains of this association are abundant in the ash. They appear opaque white under a binocular microscope. This association includes various textures: pseudomorphic replacement of original volcanic rock textures Fig.
The grains are composed of silica minerals, minor pyrite, and rutile. The pseudomorphic textured grains preserve the original volcanic rock textures, although the original minerals have been completely replaced, mostly by silica mineral. The grains are rich in voids that are spherical, tabular, veinlet, and irregular in shape. Pyrite crystals frequently fill the voids and the cleavage of the pseudomorphs of phenocrysts Fig. The pores in the highly porous grains are spherical, tabular, vein-like and irregular in shape and range from several hundred to just a few micrometers Fig.
The grains with colloform texture consist of micron-width wavy bright bands and darker matrix on BEI Fig.
The colloform grains contain void veins and irregular-shaped pores Dong et al. Grains with this assemblage appear as opaque white-colored or opaque gray-colored under a binocular microscope.
The original minerals have been completely replaced by silica mineral, alunite, kaolin-group mineral, rutile, and pyrite through hydrothermal alteration. The grains are classified into three types according to textures: pseudomorphic volcanic texture, fine-grained texture, and coarse mosaic texture.
Grains with pseudomorphic volcanic texture are rich in vugs and preserve textures of the original volcanic rocks that are porphyritic, hyalo-ophitic, or hyalopilitic. Some vugs are rectangular in shape, indicating that the original crystals had been shed during the alteration, although some crystals have been replaced by silica mineral or kaolin Fig.
Pyrite and alunite crystals fill some of the vugs and cleavages of the pseudomorphic crystals. Grains with fine-grained texture show no sign of original rock texture but merely consist of fine-grained crystals. Flaky or massive crystals of alunite fill some of the voids.
The association of silica minerals, pyrophyllite, and pyrite is common, occurring as opaque gray-colored or transparent grains. The original texture is completely lost and the original minerals have been replaced by silica mineral, pyrophyllite, pyrite, and minor rutile. Some grains comprise anhedral silica crystals and fine-grained matrix of pyrophyllite Fig. Some silica grains contain abundant micron-sized spherical pores. The matrix pyrophyllite occurs as an aggregate of fine flaky crystal or very fine spongy texture dotted with euhedral pyrite crystals.
The very fine matrix contains alligatoring voids. Some pyrophyllite-bearing grains consist solely of very fine-grained pyrophyllite with such voids. The association of silica mineral—muscovite is common in the ash. The ash grains appear as opaque white grains under a binocular microscope. The original rock texture has been lost, and the minerals have been totally replaced by a mixture of fine crystals of silica mineral, muscovite, pyrite, and rutile. A peculiar muscovite-bearing grain, which appears as a translucent brownish gray-colored grain, contains chlorite and K-feldspar.
The grain consists of coarse equant crystals of silica mineral, K-feldspar, and albite, forming equigranular texture, partly replaced by diffusively mottled chlorite and muscovite Fig. The association of silica mineral—K-feldspar—albite—garnet occurs commonly in the ash. Grains with this assemblage appear as translucent white under a binocular microscope.
Grains in this association are subdivided two types based on textures: the colloform texture Dong et al. The colloform texture consists of K-feldspar-rich bands and a fine-grained mixture of silica mineral and K-feldspar. The original texture has completely disappeared through replacement of altered minerals.
The equigranular grains contain flaky biotite crystals in pores of the K-feldspar. Free pyrite crystals are common in all size fractions. Euhedral pyrite crystals typically form aggregates ranging in size from a few micrometers to millimeters. Anhydrite-bearing grains are only observed in the medium fraction. The volcanic ash is characterized by abundant hydrothermally altered rock fragments with different degrees of alteration and hydrothermally precipitated minerals.
Juvenile material such as pumice, scoria, or glass shard was not found in the volcanic ash, whereas partly altered fragments consisting of primary igneous minerals plagioclase, orthopyroxene, titanomagnetite, and feldspars , volcanic glass, and alteration minerals are common.
Therefore, we conclude that the Ontake eruption was a non-juvenile eruption. Not all feldspars in the ash originate from fresh volcanic rock: Some were derived from the alteration zones. Other than the remnant primary minerals, the volcanic ash contains quartz, tridymite, cristobalite, kaolin-group mineral, alunite, anhydrite, gypsum, pyrophyllite, muscovite, chlorite, K-feldspar, biotite, rutile, garnet, pyrite, and smectite.
The mineral assemblage is typical of hydrothermal alteration zones in magmatic-hydrothermal systems under subduction zone volcanoes Rye et al.
The mineral assemblages therefore indicate that the volcanic ash was derived from a subvolcanic hydrothermal system developed beneath the edifice of Ontake volcano. The ash also contains free crystals of sulfide and sulfate minerals.
0コメント