Obsidian is a natural glass, often formed in volcanoes. It has a smooth glassy texture, and will commonly fracture with a curved fracture plane called conchoidal fracture, after the resemblance to the shape of a shell. Usually black because of the trace iron content.
Obsidian is formed when lava cools very quickly, typically within a few hours, preventing crystallization. This rapid cooling prevents mineral crystals from forming, resulting in a smooth, glassy texture.
Both coal and obsidian are types of rocks that are formed from cooling molten material. However, coal is primarily composed of organic matter such as plant material, while obsidian is a naturally occurring volcanic glass with a dark color and smooth texture.
Obsidian has a glassy texture because it forms from rapidly cooling lava without much time for crystal growth. This quick cooling process prevents the formation of crystals, resulting in a smooth and reflective surface similar to glass.
Obsidian is a natural glass that can form sharp edges when broken, known as obsidian flakes. However, whether it flakes in your hand would depend on the force applied and the specific condition of the obsidian. Generally, obsidian will flake if enough pressure is applied to break it.
Obsidian, or "volcanic glass," is made when molten rock comes out of a volcano and cools so quickly that no crystalline structure has time to form. This makes obsidian an extrusive igneous rock. The cooling occurs right at the surface.
Obsidian is an extrusive rock that cooled very rapidly without forming crystals. As a result, obsidian has a smooth, shiny texture of a thick piece of glass.
obsidian
Obsidian: Its texture is glassy. Obsidian is extrusive or volcanic, because the instantaneous cooling that produces such rocks is a surface phenomenon. Obsidian is amorphous, so, unlike true rocks, it is not composed of minerals.
Obsidian
Obsidian rock is simply cooled liquid magma or "lava". Obsidian rock is jet black with a very smooth texture and glossy appearance.
Very smooth rocks are called "polished rocks" or "river rocks" due to the smooth texture achieved from erosion in water bodies like rivers and oceans.
The rock you are describing is likely obsidian. Obsidian is a naturally occurring volcanic glass formed during rapid cooling of lava. It is usually black in color and has a smooth, glassy texture.
The igneous rock you are describing is likely obsidian. Obsidian is a naturally occurring volcanic glass formed from the rapid cooling of molten lava. Its smooth, glassy texture and black color make it a popular material for decorative items and tools.
Obsidian is a type of volcanic glass formed from quickly cooled lava, so it does not have layers of banding like sedimentary rocks. Instead, obsidian typically has a smooth, uniform texture with occasional swirls or flow lines caused by the rapid cooling process.
Smooth glassy lava is called obsidian. It forms when lava cools quickly, preventing crystals from forming, resulting in a glassy texture. Obsidian is typically black in color but can also appear in various shades of brown, green, or red.
Obsidian does not have cleavage because of the way it forms. Obsidian is essentially nature's form of glass and so it has no regular or patterned crystal structure. Without that crystal structure, there is no cleavage.
Obsidian is an igneous rock that has a smooth glass-like texture. It is formed when lava cools rapidly without crystal formation, resulting in a glassy texture.