Hexagonal

Definition

Hexagonal refers to a crystal system characterized by six-sided symmetry, where the crystal structure is defined by three equal axes in one plane and a perpendicular axis that is different in length. This symmetry leads to distinctive geometric shapes in the arrangement of atoms, contributing to unique physical properties and behaviors of minerals that belong to this system. Hexagonal crystals are prevalent in various minerals and have significant implications for their identification and classification.

5 Must Know Facts For Your Next Test

1. Hexagonal crystals can be further divided into two subcategories: hexagonal and trigonal, based on their symmetry and atomic arrangements.
2. Common examples of hexagonal minerals include quartz, beryl, and graphite, each exhibiting unique physical characteristics tied to their crystal structure.
3. In hexagonal systems, the axial ratio is important; the lengths of the three axes are equal in length but can differ from the length of the vertical axis.
4. Hexagonal symmetry can lead to unique optical properties in crystals, such as birefringence, which affects how light passes through them.
5. Hexagonal crystals tend to form prismatic shapes and can appear in both well-defined and more irregular forms depending on environmental conditions during their formation.

Review Questions

• How does the hexagonal crystal system differ from other crystal systems in terms of symmetry and atomic arrangement?
  • The hexagonal crystal system is distinct because it features six-sided symmetry with three equal axes in one plane and one axis perpendicular to that plane. In contrast to other systems like cubic or tetragonal, which have different arrangements and symmetry characteristics, hexagonal systems focus on this unique spatial configuration. The specific arrangement of atoms within hexagonal structures influences their physical properties and behaviors in notable ways.
• Discuss the significance of hexagonal minerals in mineral identification and classification processes.
  • Hexagonal minerals play a crucial role in mineral identification because their specific crystal structures can provide essential clues about their identity. The distinct shapes associated with hexagonal crystals—such as prisms and plates—are often key indicators during classification. By observing these forms along with other characteristics like hardness and luster, geologists can effectively categorize minerals into their respective systems, including the hexagonal category.
• Evaluate the impact of environmental conditions on the formation of hexagonal crystals, providing examples of how variations can affect their properties.
  • Environmental conditions significantly influence the formation of hexagonal crystals, including factors such as temperature, pressure, and chemical composition. For instance, quartz may form large well-defined hexagonal prisms under stable conditions, while rapid changes can result in more irregular shapes or smaller crystals. These variations can alter physical properties like cleavage patterns and optical behavior, demonstrating how crucial the environment is in determining the final characteristics of hexagonal minerals.

Related terms

Crystal Lattice: The three-dimensional arrangement of atoms or molecules in a crystalline solid, forming the basis for the crystal structure.

Mineral Identification: The process of determining the specific characteristics of a mineral, often based on its crystal structure, hardness, luster, and color.

Triclinic: A crystal system with three unequal axes that are not perpendicular to each other, contrasting with hexagonal symmetry.