Igneous Rock Identification - Viewing samples

Front

What is a porphyritic texture in igneous rocks?

Back

A porphyritic texture is characterized by large crystals (phenocrysts) embedded in a finer-grained matrix, indicating a two-stage cooling process.

Front

What type of igneous rock is granite classified as?

Back

Granite is classified as an intrusive igneous rock, meaning it forms from magma that cools slowly beneath the Earth's surface.

Front

What is the difference between extrusive and intrusive igneous rocks?

Back

Extrusive igneous rocks form from lava that cools quickly on the Earth's surface, while intrusive igneous rocks form from magma that cools slowly underground.

Front

What does coarse-grained texture in igneous rocks indicate about the cooling process?

Back

Coarse-grained texture indicates that the magma cooled slowly, allowing large crystals to form.

Front

What are vesicles in igneous rocks?

Back

Vesicles are small cavities or bubbles in volcanic rock formed by the escape of gas during solidification.

Front

How can you identify an igneous rock that cooled on the surface?

Back

An igneous rock that cooled on the surface typically has vesicles (air bubbles) and very small or no crystals.

Front

What is basalt and how does it form?

Back

Basalt is an extrusive igneous rock that forms from the rapid cooling of lava at the Earth's surface, resulting in a fine-grained texture.

Front

What is the significance of color in identifying igneous rocks?

Back

The color of igneous rocks can indicate their mineral composition; for example, dark-colored rocks are often mafic, while light-colored rocks are felsic.

Front

What is the role of cooling rate in the formation of igneous rocks?

Back

The cooling rate of magma or lava affects the crystal size in igneous rocks; slow cooling results in larger crystals, while rapid cooling results in smaller crystals.

Front

What is gabbro and how does it differ from granite?

Back

Gabbro is an intrusive igneous rock that is darker and denser than granite, containing more mafic minerals.