Characteristics of Amphibole Minerals

• Crystal Structure: Amphibole minerals have a double-chain silicate structure, which gives them their characteristic prismatic shape.
• Cleavage: They exhibit two directions of cleavage at approximately 60 and 120 degrees, which distinguishes them from other minerals.
• Color: Amphibole minerals can range in color from colorless to dark green or black, depending on their chemical composition.
• Hardness: They have a hardness ranging from 5 to 6 on the Mohs scale.
• Composition: The general chemical formula for amphibole minerals is complex, but they are primarily composed of silicon, oxygen, and various cations such as magnesium, iron, aluminum, and others.

Common Types of Amphibole Minerals

1. Hornblende: This is a common and widely distributed amphibole mineral, typically found in igneous and metamorphic rocks. It is usually black or dark green in color.
2. Actinolite: Actinolite is a green amphibole mineral that is commonly found in metamorphic rocks, particularly those subjected to low-grade metamorphism.
3. Cummingtonite: Cummingtonite is a brown to black amphibole mineral often found in high-temperature metamorphic rocks and some igneous rocks.
4. Anthophyllite: This amphibole mineral is typically light to dark brown and is found in metamorphic rocks, particularly those that have undergone high-temperature metamorphism.

Significance in Geology

Study Guide for Amphibole Minerals

1. Understand the crystal structure and cleavage patterns that are characteristic of amphibole minerals.
2. Learn to distinguish between the common types of amphibole minerals based on their physical properties and chemical compositions.
3. Explore the geological significance of amphibole minerals and how they can be used to interpret the conditions of rock formation and metamorphism.
4. Practice identifying amphibole minerals in hand samples and thin sections under a petrographic microscope.
5. Review the factors that influence the formation of amphibole minerals and the environments in which they are commonly found.

[Amphibole] Related Worksheets and Study Guides:

• Minerals IIEarth Science • High School