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Actually, obsidian doesn't have grains at all. Technically obsidian is a glass, which means it has no internal structure. When geologists refer the the grain size of a rock, they mean how big the crystals that make it up are. Since obsidian has no crystals, it therefore has no grain size.
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Does obsidian have a large grain size or a small grain?
Obsidian has a small grain size due to its volcanic origin, which means that it cools quickly and does not have time to form large crystals. It is typically fine-grained and exhibits a glassy appearance.
What is an extrusive igneous rock that is actually glass?
Obsidian is an extrusive igneous rock that forms when lava cools quickly and solidifies into a glass-like material without crystal formation. It is typically black in color and has a smooth, glassy texture due to its rapid cooling process.
Did obsidian cool quickly or slowly?
Obsidian cooled very quickly. It's a vulcanic glass, meaning that the crystals are so small, they had virtually no time to form an orderly crystalline texture, and are basically placed randomly. Smaller grain size is associated with faster cooling.
What is a black volcanic rock with small crystals?
The black volcanic rock with small crystals is most likely basalt. Basalt is fine-grained and is commonly found in volcanic regions as a result of solidified lava flows. The small crystals are often composed of minerals such as plagioclase and pyroxene.
Why are mineral crystals in obsidian too small to see without a microscope?
Obsidian cools rapidly, preventing large crystals from forming. As a result, the mineral crystals are too small to be seen with the naked eye. The rapid cooling process hinders the growth of crystals, resulting in a smooth and glassy texture.
Does obsidian have a large grain size or a small grain?
Obsidian has a small grain size due to its volcanic origin, which means that it cools quickly and does not have time to form large crystals. It is typically fine-grained and exhibits a glassy appearance.
What is an extrusive igneous rock that is actually glass?
Obsidian is an extrusive igneous rock that forms when lava cools quickly and solidifies into a glass-like material without crystal formation. It is typically black in color and has a smooth, glassy texture due to its rapid cooling process.
Smooth glassy rock that is formed when lava cools?
Obsidian
Explain pegmatite is coarse grained with large crystals basalt is fine grained with small crystals and obsidian has no crystals?
Crystal size in these rock types is determined by their rate of cooling. Pegmatites have large crystals due to very slow cooling. Obsidian has microscopic crystals due to almost instantaneous cooling.
Did obsidian cool quickly or slowly?
Obsidian cooled very quickly. It's a vulcanic glass, meaning that the crystals are so small, they had virtually no time to form an orderly crystalline texture, and are basically placed randomly. Smaller grain size is associated with faster cooling.
What is a black volcanic rock with small crystals?
The black volcanic rock with small crystals is most likely basalt. Basalt is fine-grained and is commonly found in volcanic regions as a result of solidified lava flows. The small crystals are often composed of minerals such as plagioclase and pyroxene.
Why are mineral crystals in obsidian too small to see without a microscope?
Obsidian cools rapidly, preventing large crystals from forming. As a result, the mineral crystals are too small to be seen with the naked eye. The rapid cooling process hinders the growth of crystals, resulting in a smooth and glassy texture.
Which type of rock that will have small crystals if cooled rapidly?
Igneous rocks will have small crystals if they cool rapidly. This is because rapid cooling does not allow enough time for large crystals to form. Examples of igneous rocks that exhibit small crystals due to rapid cooling include basalt and obsidian.
What igneous rock cooled the most rapidly?
Igneous rocks with very small or no visible crystals are formed by rapid cooling. A good example would be obsidian (which is a volcanic glass) and BAsalt which may have an aphanitic texture (crystals to small to see with the naked eye).
The british policy of combining many small into one large farm is known as?
small scale grain production
What is the weight of obsidian?
The weight of obsidian is approximately 2.3 to 2.6 grams per cubic centimeter.
What are small dark glassy objects from meteorites called?
Tektites
