Geological & Scientific Properties | Angelite
Angelite, also known as anhydrite or angel stone, is a mineral that's valued both for its serene aesthetic appeal and its interesting geological properties. Here's a detailed overview of Angelite:
Chemical Composition and Structure:
- Composition: Angelite is primarily composed of calcium sulfate (CaSO₄), which is also the composition of anhydrite.
- Crystal System: It crystallizes in the orthorhombic system, characterized by three mutually perpendicular axes that are of unequal length.
Physical Properties:
- Color: Angelite is known for its soft, blue to lilac-blue color, which is often uniform throughout the stone.
- Hardness: It is relatively soft compared to many gemstones, with a hardness of 3 to 3.5 on the Mohs scale.
- Luster: Angelite typically has a vitreous to pearly luster.
- Transparency: This mineral can range from translucent to opaque.
- Cleavage and Fracture: Angelite has good cleavage in one direction and fractures unevenly.
Optical Properties:
- Refractive Index: Angelite has a refractive index in the range of 1.570 to 1.613.
- Birefringence: As an orthorhombic mineral, angelite exhibits birefringence (double refraction).
Geological Occurrence:
- Formation: Angelite is formed from the alteration of calcium-rich sulfates, typically gypsum or celestite. It often forms in evaporite deposits where large bodies of water have evaporated.
- Associated Minerals: It can be found associated with minerals such as gypsum, halite, and sulfur.
Major Deposits:
- Significant deposits of Angelite are found in Peru, Mexico, Germany, Poland, Libya, Egypt, and parts of the United States.
In geology, Angelite is studied for its formation processes and mineral associations, which can provide insights into the environmental conditions of the areas where it is found. Its unique color and soft texture make it a favorite among collectors and enthusiasts of minerals.
