Question

Amphiboles and pyroxenes are both silicate minerals that form with the silicon-oxygen tetrahedron in chains. One way they can be distinguished from each other is that:

a) Pyroxene's black to dark green color
b) Both minerals can have a hardness of 5.5.
c) Pyroxene has fracture while amphibole has cleavage
d) Pyroxenes have cleavage in two directions at right angles while amphiboles have cleavage in two directions at 56° and 124°.

Answer 1

Amphiboles and pyroxenes can be distinguished from each other by their cleavage angles, with amphiboles having cleavage at 56° and 124°, and pyroxenes showing cleavage in two directions at 90 degrees.

Step-by-step explanation:

Amphiboles and pyroxenes are both types of silicate minerals that are important constituents of some igneous rocks. They can be distinguished by their cleavage angles. While both can have similar colors and hardness, pyroxenes typically show cleavage in two directions at right angles (90 degrees), which is a distinguishing factor. Conversely, amphiboles, like Hornblende, exhibit cleavage in two directions at approximately 56° and 124°, making the cleavage angle an essential diagnostic feature to differentiate between these two minerals.

Correctly identifying whether a rock contains amphibole or pyroxene can provide valuable insights into its geologic history and the conditions under which it formed. For instance, knowing the specific cleavage of these minerals allows geologists to determine the mineral composition of a rock sample, which in turn reveals the rock's classification and formation environment.