Definition

1. Adjective:
   • Exhibiting pleochroism: Describes a substance, typically a crystal, that appears to show different colors when viewed from different directions under transmitted light. This optical property is due to the differential absorption of light waves depending on their vibration direction relative to the crystal's structure.

Usage Examples

• Adjective:
  • Tourmaline is a classic example of a pleochroic mineral.
  • Under the polarizing microscope, the pleochroic crystal displayed shades of brown and green.
  • Gemologists must consider the pleochroic nature of a stone when determining the optimal cutting direction.

Advanced Usage

• "Strongly pleochroic": Used to describe a material where the color change is very pronounced and easily observable.
  • Cordierite is strongly pleochroic, shifting from violet-blue to pale yellow.
• "Pleochroic halo": A term in geology and mineralogy referring to a microscopic, colored ring or sphere of radiation damage in a mineral, caused by the inclusion of a radioactive particle.
  • The pleochroic halos in the biotite were evidence of its ancient exposure to radioactive elements.

Variants and Related Words

• Pleochroism (n): The optical phenomenon itself, where a substance shows different colors from different angles.
  • The gem's value is enhanced by its distinct pleochroism.
• Dichroic (adj): A specific type of pleochroism where a crystal shows two different colors or shades. (Note: All dichroic materials are pleochroic, but not all pleochroic materials are dichroic; some may show three colors—trichroic).
  • The dichroic filter reflects one color while transmitting another.

Synonyms

• Polychroic: Having or exhibiting many colors (a less common synonym).
• Color-variable: A descriptive, non-technical term for the property.

Related Terms (Not Phrasal Verbs)

• Anisotropic: A broader term for materials whose physical properties (including optical ones like pleochroism) vary with direction.
• Absorption: The process by which a material takes in light energy, which is the underlying cause of pleochroism.

Adjective

1. of or relating to or having pleochroism