Lab Exam 1: Intro to Earth Science: Igneous Rocks

• Light‐colored silicates• Minerals• Feldspar (K or Na)• Silica (quartz)• Composes continentalcrust

• Dark silicates andcalcium‐rich feldspar• Minerals• Magnesium• Ferrum (iron)• Composes oceanic crust

Cool very slowly beneath the surface of the earth.Crystals have time to grow to large sizes (1mm +)

Cool very rapidly at the surface of the earth.Doesn’t allow time for large crystals to developComposed of tiny crystals and/or glass

• Individual crystals arevery small or not visible(< 1mm)

• Large crystals surroundedby small crystals• 2 different cooling rates

• Solid glassy mass• Conchoidal fracture• Really fast cooling

• Contains air bubbles• Escaping gas

A fine-grained igneous rock that is usually black in color.

A light-colored vesicular igneous rock. It forms through very rapid solidification of a melt. The vesicular texture is a result of gas trapped in the melt at the time of solidification.

A dark-colored, vesicular, extrusive igneous rock. The vesicles are a result of trapped gas within the melt at the time of solidification. It often forms as a frothy crust on the top of a lava flow or as material ejected from a volcanic vent and solidifying while airborne.

a fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene and biotite.

a coarse-grained intrusive igneous rock that is composed almost entirely of olivine. It may contain small amounts of amphibole, feldspar, quartz or pyroxene.

A coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene, hornblende and sometimes quartz.