Hexagonal

Definition

Hexagonal refers to a crystal system characterized by a unique six-sided symmetry and specific axial relationships. This system allows for the formation of crystals that have a hexagon-shaped base and includes various minerals that exhibit this structure, resulting in distinctive physical properties and behaviors. Understanding the hexagonal system is essential for recognizing how these structures fit into the broader context of crystal systems and mineral classification.

5 Must Know Facts For Your Next Test

1. The hexagonal crystal system is defined by four axes: three of equal length intersecting at 120 degrees in one plane, and a fourth axis of a different length perpendicular to this plane.
2. Common minerals that crystallize in the hexagonal system include quartz, calcite, and beryl, each exhibiting unique physical properties due to their crystal structure.
3. Hexagonal crystals can form elongated shapes known as prismatic crystals or occur as hexagonal plates, each influencing their appearance and behavior.
4. The symmetry of hexagonal crystals plays a significant role in determining their optical properties, including how they interact with light.
5. Hexagonal close packing is an important concept in solid-state chemistry where spheres are arranged in a hexagonal lattice for maximizing density.

Review Questions

• How does the hexagonal crystal system differ from other crystal systems in terms of symmetry and axial relationships?
  • The hexagonal crystal system is distinct from other systems primarily due to its unique arrangement of axes. It features four axes where three are equal in length and meet at 120 degrees in one plane while the fourth axis is perpendicular and of a different length. This specific arrangement creates a six-sided symmetry not found in other systems such as cubic or tetragonal. The geometric characteristics of these axes lead to unique crystal shapes and properties specific to the hexagonal system.
• Discuss the significance of common minerals like quartz and calcite within the hexagonal crystal system and how their structures influence their properties.
  • Quartz and calcite are significant examples of minerals within the hexagonal crystal system. Their hexagonal structure influences their hardness, cleavage, and optical characteristics. For instance, quartz is known for its hardness and resistance to weathering due to its tightly packed atomic structure, while calcite exhibits distinct cleavage patterns along its planes. Understanding these relationships helps in identifying minerals and predicting their behavior in various geological processes.
• Evaluate the impact of hexagonal close packing on the properties of materials within solid-state chemistry.
  • Hexagonal close packing (HCP) is a critical arrangement in solid-state chemistry that maximizes density among spheres arranged in a hexagonal lattice. This packing arrangement influences properties such as stability, strength, and conductivity of materials. For example, metals that adopt HCP structures often demonstrate enhanced mechanical strength compared to those with other arrangements due to the optimal spatial efficiency of atom placement. Understanding HCP is essential for material scientists aiming to design materials with desired physical properties for various applications.

Related terms

Crystal System: A classification method for minerals based on their internal symmetry and lattice parameters, including cubic, tetragonal, hexagonal, orthorhombic, monoclinic, and triclinic systems.

Lattice: The regular arrangement of atoms, ions, or molecules in a crystalline solid, which defines its structure and determines its properties.

Dichroism: A property observed in some crystals where they exhibit different colors when viewed from different angles due to variations in light absorption.