Obsidian exhibits what type of texture

The combination of black and brown colours — the mahogany obsidian — is the most abundant. An obsidian with white, radially concentric flakes of cristobalite, named the flocullent obsidian, is the product of partial crystallization of a metastable glass. Obsidians can also rarely contain a larger amount of inclusions small rock fragments, crystals, gas vesicles which reflect the light and create a variegated play of lights.

This kind of obsidian is designated as iridescent, silver, or golden according to the colour of the gloss. Extremely rare is a flaming obsidian, which is relatively clear, but glaring colours originate inside it as a result of the light reflection from very thin layers. Obsidian most frequently originates by a rapid coooling of a felsic viscous lava. Diffusion in the very viscous acid and felsic lavas with highly polymerized SiO 2 tetrahedrons is slow, thus inhibiting the nucleation of crystals and supporting the origin of the glassy structure.

Obsidian is fragile, tough and it disintegrates to very sharp slivers. Name origin The name obsidian is very ancient. It is ascribed to Theophrastus who used it for the first time in BC. The name origin is not fully elucidated. Major minerals Amorphous volcanic glass that exhibits the structural ordering similar to crystals only in very short distances. For this reason, the obsidian is sometimes regarded as a mineraloid. Classification Volcanic rocks containing more than 80 vol.

However, individual types of volcanic glasses also differ in terms of their structure and texture. The obsidian from the Lipari Island corresponds to the rhyolite glass. Petrographic characteristics Unaltered compact obsidian with black colour, pronounced conchoidal fracture and sharp edges. It does not contain any macroscopically discernible inclusions of gases, liquids or solids, such as minerals or rock fragments. The obsidian exhibits a pronounced vitreous lustre.

It does not scratch glass, thus corresponding to the hardness of 5 or 6 in the Mohs scale. It is translucent in thin cleavage fragments and along sharp margins. Most limestone has a biochemical origin. Compaction is most significant as a lithification process for sedimentary rocks composed of sand-sized particles. During metamorphism the material undergoing deformation remains a solid. The single most characteristic feature of sedimentary rocks is strata or beds.

The largest quantity of metamorphic rock is produced by regional metamorphism. Slate is associated with high-grade metamorphism. Metamorphism is commonly associated with mountain building. Metamorphism can affect only sedimentary rocks.

Which of the following is the process of getting oxygen from the environment to the tissues of the body? Total word count: Pages: 4. Get Now. Calculate the Price Deadline. Paper type Essay Pages - - words. Looking for Expert Opinion? An igneous rock that contains vesicles: a is also extrusive b is also fine grained c contains many small holes d all of the above d all of the above As the rate of cooling increases, the size of the crystals that form: decreases Which one of the following is an igneous rock?

Glassy Rocks that contain crystals that are roughly equal in size and can be identified with the unaided eye are said to exhibit what kind of texture? Porphyritic Rhyolite is the fine-grained equivalent of this igneous rock. Granite Select the coarse-grained rock which is composed mainly of quartz and potassium feldspar from the list below: a basalt b andesite c granite d diorite Granite This rock gets its name from a chain of mountains located in South America.

Andesite Which of the rocks listed below is a popular building stone? Foliation Which of the following changes may occur during metamorphism? Quartzite The agents of metamorphism are? False Olivine and quartz are commonly found together in the same rock. False One magma can produce several different igneous rocks having different mineral compositions.

True Basalt is the fine-grained equivalent of gabbro True Glassy igneous rock form when magma cools too fast for mineral grains to grow. True Quartz is quite resistant to weathering and is an important component of sand in riverbeds and on beaches. True Like most other liquids, water decreases in volume when it freezes.

False The particles in breccia are primarily silt sized. False The most abundant sedimentary rock is shale. True Evaporites have a biochemical origin. False Particle size is the primary basis for distinguishing among various detrital sedimentary rocks. True Most limestone has a biochemical origin. True Compaction is most significant as a lithification process for sedimentary rocks composed of sand-sized particles. False During metamorphism the material undergoing deformation remains a solid True The single most characteristic feature of sedimentary rocks is strata or beds.

True The largest quantity of metamorphic rock is produced by regional metamorphism. The rapid cooling of lava results in a fine-grained texture, or in this case with obsidian , a glassy texture, where cooling takes place so rapidly that mineral crystals do not have time to form. Rock that is formed from slow cooling magma beneath the surface is intrusive igneous rock, and exhibits visible mineral crystals.

Obsidian is an extrusive igneous rock. Gabbro is Coarse-grained while obsidian is Glassy non-crystalline. Pure obsidian actually has a glassy texture grain , with no discernible crystalline structure.

Obsidian rock is simply cooled liquid magma or "lava". Obsidian rock is jet black with a very smooth texture and glossy appearance. An obsidian rock is an extrusive igneous rock that forms when a volcano erupts and has no time to crystallize, so it has a glassy texture. Obsidian rocks are generally black in color. The texture is really glassy, like obsidian.

Obsidian is not identified, classified, or described by height. It is described by its texture, fracture, hardness, and chemical composition. Obsidian is an glassy, extrusive, igneous rock that is found in areas that have experienced rhyolitic eruptions. Obsidian is formed when the rhyolitic lava comes into contact with water.

This quick-cooling results in the glassy texture of obsidian. Log in. Earth Sciences. Study now. See Answer. Best Answer. Study guides. Earthquakes 20 cards. How often do meteorites hit Earth. The adjustments of materials that follow a major earthquake often generate smaller earthquakes called.

Most earthquakes are produced by the rapid release of which kind of energy stored in rock subjected to great forces. What does an earthquake's magnitude measure. Astronomy 20 cards. How do scientists study the Layers of the Earth. What type of volcanoes formed the Hawaiian islands. Which type of fault is the San Andreas fault. Which type of volcano produces volcanic bombs.

Meteorology and Weather 20 cards.