how to tell if rock is vesicular or course

You want to look for any type of metallic appearance or streamlined flow structures. Rocks that have a metallic appearance with a scaly or smooth texture are metamorphic. Igneous rocks may have a vesicular texture. This is when the rock appears to be very porous with many holes. Pumice is an example of a rock that has a very porous texture.

Full Answer

What are vesicles in rocks?

The Dictionary of Geologic Terms (1984, R. Bates & J. Jackson, eds.) defines vesicle as “a small cavity in an aphanitic or glassy igneous rock, formed by expansion of a bubble of gas or steam during solidification of the rock.” Such a rock is said to be vesicular. Only igneous rocks – rocks that cooled from a molten magma – can have vesicles.

What is the difference between a vesicular and a meteorite?

If you have a vesicular rock that does not have a fusion crust, then it is not a meteorite. The Dictionary of Geologic Terms (1984, R. Bates & J. Jackson, eds.) defines vesicle as “a small cavity in an aphanitic or glassy igneous rock, formed by expansion of a bubble of gas or steam during solidification of the rock.”

What is the difference between vesicular igneous and pyroclastic igneous rocks?

Vesicular igneous rocks, such as pumice, look bubbly and form before gases are able to escape as lava forms the rock. This also formed with very rapid cooling. Pyroclastic igneous rock is a texture composed of volcanic fragments ranging from very fine (ash) to very coarse (tuffs and breccias).

How do you identify igneous rocks with glassy texture?

You will need to use a magnifying glass to observe the crystals in aphanitic rocks. Igneous rocks that form too quickly for crystals to form have what is called a glassy texture. Obsidian is the only glassy igneous rock, and can be identified by its dark color.

How do you know if a rock is coarse?

Grain Size: Coarse grains are visible to the naked eye, and the minerals can usually be identified without using a magnifier. Fine grains are smaller and usually cannot be identified without using a magnifier.

What makes a rock vesicular?

Vesicles are the small holes left behind after lava cools and turns into volcanic rock. Vesicles help geologists understand the cooling history of extrusive (volcanic rocks) because lava contains large amounts of dissolved gases that are released as the lava hardens.

What rocks are vesicular?

Vesicles only develop in rocks that cool from a liquid – an igneous rock. Most meteorites come from asteroids, and almost all asteroids are too small to have volcanoes, thus few meteorites are igneous rocks. Most such rocks among the meteorites are basalts.

What does vesicular rock look like?

Vesicles are fossil bubbles. So, a rock that looks like Swiss cheese has a vesicular texture. Vesicles range in shape from spherical to elongated and in size from ~1mm to more than 1 cm. Basalts are most commonly vesicular.

What igneous rocks are vesicular?

Vesicular texture -- basalt scoria: This is an extrusive igneous rock that chilled very quickly, so that the bubbles (vesicles) formed by escaping gas were preserved.

What makes an igneous rock vesicular texture?

Vesicular texture refers to volcanic rocks that contain holes called vesicles that were formed by gas bubbles in lava. This igneous rock is called scoria. It has vesicular texture. The vesicles form from escaping gas bubbles in cooling lava.

Is granite vesicular or non vesicular?

Classification of Igneous RocksTEXTUREFelsicUltramaficPhaneriticGranitePeridotiteAphaniticRhyoliteVesicularPumiceGlassyObsidian1 more row

Is Obsidian vesicular or non vesicular?

Vesicular basaltic volcanic glass from Punalu'u Beach, Hawaii. Width of view 20 mm. Obsidian with gray layers of rhyolitic pumice in Long Valley Caldera in California. Pumice and rhyolite have very similar composition but they differ in texture — pumice is highly vesicular while obsidian is massive.

What does vesicular texture indicate?

Vesicular texture occurs when gases are trapped within a lava flow and minerals crystallize around the gas pocket. Pyroclastic texture results from explosive volcanic eruptions and the resulting rock is composed of a mixture of preexisting igneous rock, mineral grains, and ash particles.

What is coarse grained texture?

(a) Said of a crystalline rock, and of its texture, in which the individual minerals are relatively large; specif. said of an igneous rock whose particles have an average diameter greater than 5 mm (0.2 in.).

Can extrusive rocks be vesicular?

extrusive igneous rocks Such openings are called vesicles, and the rocks in which they occur are said to be vesicular.

What does vesicular basalt look like?

Vesicular basalt is a dark-colored volcanic rock that contains many small holes, more properly known as vesicles. A vesicle is a small cavity in a volcanic rock that was formed by the expansion of a bubble of gas that was trapped inside the lava.

What does vesicular texture indicate?

Vesicular texture occurs when gases are trapped within a lava flow and minerals crystallize around the gas pocket. Pyroclastic texture results from explosive volcanic eruptions and the resulting rock is composed of a mixture of preexisting igneous rock, mineral grains, and ash particles.

How is vesicular basalt formed?

Vesicular basalt is formed when magma erupts from a volcano in the form of lava and it quickly hardens.

Can extrusive rocks be vesicular?

extrusive igneous rocks Such openings are called vesicles, and the rocks in which they occur are said to be vesicular.

What causes vesicles to form in lava quizlet?

As the rock cools gas bubles are created as a result of disolved gasses escaping from the magma, this forms circle to oval features called vesicles. Gas rises so most vesicles are at the top of lava flow and they are sometimes elongated in the direction of flow. This texture is common in Pumice and Basalt.

How to tell what type of rock you have?

Look at your rock for signs of layering. The presence and distribution of layering can help you identify the main type of rock you have.

Which rock is bubbly and forms before gases escape?

Vesicular igneous rocks, such as pumice, look bubbly and form before gases are able to escape as lava forms the rock. This also formed with very rapid cooling.

What are phaneritic igneous rocks made of?

Phaneritic igneous rocks are composed of interlocking crystals that are smaller than crystals in pegmatitic but still visible with the naked eye.

How are igneous rocks formed?

Igneous rocks are formed by cooling magma. The location of the formation of the rock, as well as how fast the magma cools will determine the type of igneous rock. Intrusive rocks form from the cooling of magma deep beneath the earth's surface. Since this occurs below the earth's surface, the magma will cool very slowly.

What are the two types of igneous rocks?

1. Classify igneous rocks into two main types: intrusive or extrusive. Each of these types of rocks will have specific properties that will help you distinguish which type your igneous rock is. Magma is molten rock that flows beneath the earth's surface. Igneous rocks are formed by cooling magma. The location of the formation ...

How many different textures are there for igneous rocks?

Identify the texture type of your rock. There are 7 different texture classes for igneous rocks, each with their own unique features. Pegmatitic igneous rocks have very large crystals, more than 1 cm in size. These are the slowest cooling type of igneous rocks.

What type of rock has microscopic crystals?

Extrusive rocks have very small, almost microscopic crystals. These are often described as fine-grained rocks. You usually can't see these with the naked eye.

How do vesicles form?

Elongated vesicles form when the lava flows and stretches the gas bubbles before it solidifies (sawn face). Photo credit: Randy Korotev.

Why is the fusion crust strikingly vesicular?

The fusion crust (bottom) is strikingly vesicular because the meteorite is a regolith breccia. Note that here are no vesicles in the interior of the meteorite (top) because the interior did not get hot enough to melt. Centimeter cube for scale. Photo credits: NASA.

What type of basalt is found on the moon?

About 5% (I have not actually counted) of the basalt samples collected on the Apollo missions to the Moon are vesicular . At the top is sample 71155 from the Apollo 17 mission (cube is 1 cm) and at the bottom is sample 15556 from the Apollo 15 mission (cube is 2 cm) and . Note that the vesicles are round, not elongated, because lunar basaltic magmas had very low viscosity and lunar gravity is low. It is possible that someday someone will find a vesicular basaltic lunar meteorite, but so far it has not happened. Vesicular basalts may not survive the shock of being blasted off the Moon and passing though Earth’s atmosphere Photo credits: NASA.

What is the color of basalt?

It is not a meteorite fusion crust. Basalts come in a variety of colors, mostly gray or black to rust colored. Photo credit Randy Korotev

What type of rock forms when lava cools?

Vesicles in Terrestrial Rocks. Basalts and related volcanic rocks (andesites, dacites) form when volcanic lava or magma cools. Not all basalts are vesicular, but vesicular basalts are very common on Earth. Vesicular basalt.

What rocks are found in the Martian meteorites?

Most such rocks among the meteorites are basalts. Most common are the eucrites and diogenites which come from a large asteroid like 4 Vesta that had volcanoes, martian meteorites (Mars has some really big volcanoes), and about 5% of the lunar meteorites.

Why are lunar basalts not amygdaloidal?

Lunar basalts are not amygdaloidal because the Moon is so dry that there are no fluids. Some lunar meteorites contain amygdules, however, that formed after the meteorite landed on Earth (see Shi ş r 166, below). An amygdaloidal terrestrial basalt from my rock garden. Photo credit: Randy Korotev.

Igneous Rocks

Igneous rocks (fiery rocks) are made when molten material inside or outside the earth cools and becomes solid. This melted rock is called magma when it is inside the earth. When magma finds its way to the surface through cracks or volcanoes, it is called lava.

Intrusive Igneous Rocks

Feldspar (pink to white blocky mineral) crystallizes at high temperatures early in the cooling process and, thus, has straight crystal sides.

Extrusive Igneous Rocks

While molten, they flow out onto the surface or flow into cracks near the Earth's surface.

Volcanic Glass

Formed by sudden cooling with no time to form even tiny crystals. This rapid crystallization produces glass with a random arrangement of atoms, therefore, these rocks are slightly less dense. The volcanic glasses are usually from a more viscous (harder to flow) lava of rhyolite chemical composition.

Characteristics of Important Minerals in Igneous Rocks

Quartz: Occurs as irregular, glassy grains, commonly clear to smoky with no cleavage.

1. Examine The Shape

Crystals come in different shapes. While two different types of crystals can have a similar shape, the shape of a stone is the first thing to look at if you think it may be a crystal.

2. Note The Colors

Crystals come in different colors. Some crystals share the same base color as other crystals, but the color of the crystal also helps with the identification. Some common crystal colors are:

3. By the Location or Point of Collection

Certain crystals are more common in specific locations. You may not find crystals such as emerald in the same location you find jades.

4. By Their Composition

The composition of crystals is what makes them unique. Two crystals can have the same shape or color, but will not have the same composition if they are not the same type.

5. Other Accompanying Rocks

When identifying a crystal, it is also recommended to examine the rocks and impurities that were with the crystal during collection. Identifying rocks such as geodes can help with the identification.

Recommended Guides to Easily Identify Crystals

Just looking at a rock is usually not enough to tell the type of crystal that it is. You will be needing a guide to further identify the rock. Here are some great guides to help you identify crystals:

Beware of Fake Crystals

You should note that some stones or objects people share may not be crystals, or are fake crystals. Here are some ways to identify fake crystals:

What is Granite?

Hotspots are regions near the base of the crust where a plume of hot mantle material causes volcanic activity at the surface. When hotspots occur beneath oceanic crust, the resulting molten rock will often produce basaltic lavas. Examples of basalt deposits that form at hotspots include the basalt bedrock of the Hawaiian Islands.

What does basalt look like?

Basalt is usually dark grey to black in colour, due to its high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to a high content of plagioclase, and these are sometimes described as leucobasalts.

What is the distinguishing property of basalt?

Basalt Properties Distinguishing Features: Completely crystallized; very small crystals, generally invisible to the naked eye ; black or very dark gray in color; sometimes contains gas bubbles (as shown above); weathering of iron minerals can turn the surface tan or reddish brown (see below).

Is basalt smooth or rough?

'A'a basalts have rough surfaces (that make barefoot people cry, "Ah! Ah!" as they walk across it). They form from fast flowing lava. Pahoehoe basalts have a smooth glassy surface that looks like many ropes.

What does peridotite look like?

Classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green. Peridotitic outcrops typically range from earthy bright yellow to dark green in color; this is because olivine is easily weathered to iddingsite.