Question

Cleavage is the tendency of a mineral to break in a predictable manner when subjected to a force. The image below shows a calcite fragment. Which statement about calcites cleavage is true?

A. Calcite has 1 plane of cleavage
B. Calcite has 3 planes of cleavage, on of which is inclined
C. Calcite has 2 perpendicular planes of cleavage
D. Calcite has 2 inclined planes of cleavage

Answer 1

Calcite has 3 planes of cleavage, with one plane being inclined, distinguishing it with a rhombohedral cleavage pattern. Cleavage is identifiable through shiny flat surfaces using light reflections and close examination with a hand lens.

Step-by-step explanation:

The correct statement about calcite's cleavage is: B. Calcite has 3 planes of cleavage, one of which is inclined. Calcite, being the mineral calcium carbonate (CaCO3), demonstrates a classic rhombohedral cleavage pattern. This means it breaks along three different planes that are not perpendicular to each other but have characteristic angles. The unique cleavage of calcite is vital in its identification and plays a role in some of its properties like double refraction, where it can split light into two beams.

When attempting to identify cleavage in calcite or any other mineral, one can use a flashlight or sunlight to look for shiny, flat surfaces which indicate the presence of cleavage planes. Using a hand lens to examine subtle surface variations can further assist in identifying cleavage patterns, which can be more accurate than macroscopic observations alone.