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Summary: Anhedral refers to minerals that lack well-defined crystal faces or external geometric shapes due to restricted growth conditions. This term is used in mineralogy to describe the appearance and characteristics of certain minerals within rocks.

Anhedral is a term used in mineralogy and petrology to describe the lack of well-defined crystal faces or external geometric shapes in a mineral. Anhedral minerals are those that do not exhibit the characteristic crystal forms with sharp edges and distinct faces commonly associated with crystalline minerals.

Minerals can have different degrees of crystal growth and development. Anhedral minerals are those that have formed within a confined space or under conditions where they were unable to grow freely and develop their characteristic crystal faces. As a result, anhedral minerals tend to have irregular shapes and can appear as grainy or compact masses.

The term “anhedral” is often used in contrast to “euhedral,” which refers to minerals that have well-defined and characteristic crystal faces. Euhedral minerals are typically found in environments where they have had the space and conditions to grow freely without constraints.

Anhedral minerals can provide important information about the geological processes and conditions under which they formed. For example, minerals that form rapidly in a molten state (igneous rocks) or under high pressures and temperatures (metamorphic rocks) may not have had the opportunity to develop well-defined crystal faces, resulting in anhedral textures.