ASBOG Mineralogy and Petrology 5

Question 1

The Al₂SiO₅ polymorphs kyanite, sillimanite, and andalusite are distinguished from each other primarily by:

Accepted Answer

Pressure and temperature conditions of formation

Answer

The three Al₂SiO₅ polymorphs have identical chemistry but form under different P-T conditions: andalusite (low P), kyanite (high P), and sillimanite (high T).

Question 2

Which rock type is produced by the solidification of lava flows on the seafloor, characterized by pillow-shaped lobes?

Accepted Answer

Pillow basalt

Answer

Pillow basalt forms when submarine lava is rapidly chilled by seawater, creating ellipsoidal to pillow-shaped lobes with glassy rinds.

Question 3

The Mohs hardness scale assigns a hardness of 7 to which mineral, commonly used as a standard?

Accepted Answer

Quartz

Answer

Quartz (SiO₂) defines hardness 7 on the Mohs scale, scratching glass and most common minerals but being scratched by topaz (8), corundum (9), and diamond (10).

Question 4

In the classification of metamorphic rocks, a gneiss differs from a schist by:

Accepted Answer

Having compositional banding rather than continuous foliation defined by platy minerals

Answer

Gneiss is characterized by compositional banding (alternating felsic and mafic layers) and coarser grain size, while schist has continuous foliation defined by abundant aligned mica.

Question 5

Bowen's Reaction Series describes which process?

Accepted Answer

The sequential crystallization of minerals from a cooling basaltic magma

Answer

Bowen's Reaction Series outlines the continuous and discontinuous branches of mineral crystallization as basaltic magma cools, predicting which minerals form first.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG Mineralogy and Petrology 5