Earth's Processes: Rocks Online Practice

Question

Complete this assessment to review what you’ve learned. It will not count toward your grade.
13 of 1313 of 13 Items

Question
Use the table to answer the question.

Mineral

Hardness

Cleavage/Fracture

Luster

Obsidian

5

Fracture

Vitreous

Halite

2.5

Cubic cleavage

Vitreous

Fluorite

4

Octohedral

Vitreous

An unknown mineral specimen is not scratched by a penny and does not exhibit cleavage. The mineral is most likely to be:

(1 point)
Responses

obsidian
obsidian

halite
halite

fluorite
fluorite
Remaining Attempts : 3

Answer 1

To determine which mineral the unknown specimen is most likely to be, we can analyze the information provided:

1. The unknown mineral is not scratched by a penny. A penny has a hardness of about 3.5. Therefore, the mineral must have a hardness greater than 3.5.

2. The mineral does not exhibit cleavage. This suggests it must have a fracture instead.

Based on the characteristics:

• Obsidian has a hardness of 5 (greater than 3.5) and exhibits fracture, so it could match the unknown mineral.
• Halite has a hardness of 2.5 (less than 3.5), so it cannot be the mineral since it was not scratched by a penny.
• Fluorite has a hardness of 4 (greater than 3.5) but it exhibits octohedral cleavage, which means it does not match the unknown mineral since it does not exhibit cleavage.

Given these analyses, the mineral is most likely to be:

Obsidian