Metamorphic, Sedimentary, and Igneous Rock Flashcards

A set of practice Q&A flashcards covering foliated metamorphic textures, sedimentary rock classifications and formation processes, and igneous rock textures and examples.

What characterizes a foliated metamorphic rock?

Platy or elongated minerals align parallel to the axis of pressure, resulting in a layered appearance.

What is the gneissic texture?

Minerals are visible and elongated with a coarse banded appearance due to mineral alignment (e.g., in gneiss).

What does the term 'gneissic' indicate about mineral texture?

Minerals are visible and elongated, giving a coarse, banded appearance.

What does 'schistose' describe in metamorphic rocks?

Minerals are visible to the naked eye with distinct layering; common minerals include chlorite, graphite, biotite, and muscovite.

What does 'phyllitic' texture mean?

Minerals are barely visible; alignment results in foliation that is not clearly defined.

What does 'slaty' texture indicate?

Minerals are microscopic; rock may not look foliated, but it splits along parallel planes (slaty cleavage).

What is the dominant agent in foliated metamorphic rocks?

Pressure.

What is the dominant agent in crystalline (non-foliated) metamorphic rocks?

Heat; minerals change without melting.

What type of sedimentary rock forms from lithification of rock and mineral fragments?

Clastic sedimentary rocks.

Give two examples of clastic sedimentary rocks.

Breccia and Sandstone.

What sedimentary rocks form from precipitation out of solution?

Crystalline (chemical) sedimentary rocks.

Name two examples of crystalline sedimentary rocks.

Limestone and Rock Salt.

What are bioclastic sedimentary rocks?

Rocks formed from accumulation of organic material or biological activity, often containing fossils.

What is lithification?

The process by which sediments are transformed into rock through compaction and cementation.

What are the two main steps of lithification?

Compaction and Cementation.

What happens during compaction?

Sediments are pressed together under increased pressure, expelling much of the water.

What happens during cementation?

minerals precipitate to bind grains together, cementing them into rock.

What is dunite?

An ultramafic rock composed almost entirely of olivine, usually greenish in color.

What are the main components of sedimentary rocks and fossils?

They are formed from weathering products, erosion, and deposition; fossils are commonly found in sedimentary rocks.

What is color index in igneous rocks a guide to?

Composition: felsic rocks are light-colored and silica-rich; mafic/ultramafic rocks are dark and iron-rich.

Is granite intrusive or extrusive?

Intrusive (plutonic).

What is obsidian?

A volcanic glass; typically felsic in composition but very dark in color.

What textures are typical of intrusive igneous rocks?

Phaneritic (visible crystals) and Pegmatitic (very large crystals).

What textures are typical of extrusive igneous rocks?

Aphanitic (too small to see), Vesicular (gas bubbles), and Glassy (obsidian).

Name some common igneous rocks and whether they are intrusive or extrusive.

Granite (intrusive), Diorite (intrusive), Gabbro (intrusive), Basalt (extrusive), Andesite (extrusive), Obsidian (extrusive, glassy), Scoria (extrusive).

What is the overall difference in cooling between intrusive and extrusive rocks?

Intrusive rocks cool slowly underground (thousands of years) with larger crystals; extrusive rocks erupt at the surface and cool rapidly (seconds to months) with small to no crystals.