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Neither. It has no visible grain.

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Does obsidian a glassy rock have a large grain size or a small grain size?

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.


How much inches high wide and deep is obsidian?

Obsidian is a naturally occurring glass formed as an extrusive igneous rock. It is produced when acidic lava,extruded from a volcano cools very rapidly, freezing without sufficient time for crystal growth.Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where cooling of the lava is rapid.Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as stone age knives and arrowheads, and its modern use as surgical scalpel blades.Obsidian can be found as lumps of rock of any size up to and including an entire mountainside.Obsidian has several varieties. Obsidian can contain small bubbles of air that are aligned along layers created as the molten rock was flowing just before being cooled. These bubbles can produce interesting effects such as a golden sheen, known as Sheen Obsidian or a rainbow sheen called Rainbow Obsidian. Inclusions of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern producing Snowflake Obsidian. Small nuggets of obsidian that have been naturally rounded and smoothed by wind and water are called Apache Tears.Often confused with smoky quartz, obsidian has similar properties to quartz because of a similar chemistry. However, many properties dependant on a crystal structure are altered or absent in obsidian because it lacks any crystal structure of its own. The piezoelectric and optical properties in quartz are thus absent in obsidian. Smoky quartz usually has a splotchy or zoned distribution to its color while Obsidian's color is more uniformly distributed.


How does texture affect grain size in rock?

It doesn't. The grain size effects the texture. If a rock has a small grain size, it will have a smooth texture. If the grain size is large, such as pebbles, the texture will be rough. For example, siltstone is one of the smoothest rocks because it contains silt particles, which are .0004cm to .006cm. Conglomerate though contains various particles including cobbles and boulders, which are from 10cm to 100cm.


Which features tells you how large the grains of a sedimentary rock are?

The size of the grains in a sedimentary rock can be determined by examining the texture of the rock. Coarser grains indicate a larger grain size, while finer grains indicate a smaller grain size. Other features that can provide clues to grain size include the sorting (uniformity of grain sizes) and rounding of the grains.


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.

Related Questions

Does obsidian a glassy rock have a large grain size or a small grain size?

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.


What is obsidian's grain size?

there is no visible grain size


What is the grain size of dacite?

Small to medium grain size.


What is Grain size of metamorphic rock?

It varies some metamorphic rocks are fine grained (eg slate) and others have very large crystals (eg an augen gneiss).


Are meteors small?

Meteors can vary in size, ranging from as small as a grain of sand to as large as a boulder. When a meteor enters the Earth's atmosphere, it heats up and creates the glowing streak of light we see, known as a meteor or shooting star.


What is a small grain size rock?

clay


What is grain size of quartzite?

it is small depending on the colors


What are rough textured rocks?

Rocks with a large grain size perhaps with angular grain shapes.


Is obsidian found anywhere in upstate new york?

My 8 year old found a large piece of obsidian in dansville ny this weekend. We are amazed by its size and beauty


What is the size of a shale rock?

Rocks don't come in particular sizes. Shale is a type of rock - it can be as small as a grain of sand or as large as a mountain range


How much inches high wide and deep is obsidian?

Obsidian is a naturally occurring glass formed as an extrusive igneous rock. It is produced when acidic lava,extruded from a volcano cools very rapidly, freezing without sufficient time for crystal growth.Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where cooling of the lava is rapid.Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as stone age knives and arrowheads, and its modern use as surgical scalpel blades.Obsidian can be found as lumps of rock of any size up to and including an entire mountainside.Obsidian has several varieties. Obsidian can contain small bubbles of air that are aligned along layers created as the molten rock was flowing just before being cooled. These bubbles can produce interesting effects such as a golden sheen, known as Sheen Obsidian or a rainbow sheen called Rainbow Obsidian. Inclusions of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern producing Snowflake Obsidian. Small nuggets of obsidian that have been naturally rounded and smoothed by wind and water are called Apache Tears.Often confused with smoky quartz, obsidian has similar properties to quartz because of a similar chemistry. However, many properties dependant on a crystal structure are altered or absent in obsidian because it lacks any crystal structure of its own. The piezoelectric and optical properties in quartz are thus absent in obsidian. Smoky quartz usually has a splotchy or zoned distribution to its color while Obsidian's color is more uniformly distributed.


What are fine textured rocks?

They are rocks with a small grain size.