Which term denotes possessing the same physical or optical properties in all crystal directions?

Which term denotes possessing the same physical or optical properties in all crystal directions?

• A. Singly refractive (isotropic)
• B. Grain lines
• C. Habit
• D. Macle

Answer: (A)

When a crystal has the same physical and optical properties in every direction, it is isotropic. In optics, isotropic minerals are singly refractive, meaning light experiences only one refractive index regardless of the direction it travels through the crystal, so there is no double refraction. Diamond, with its cubic crystal system, is a classic example of an isotropic, singly refractive mineral. The other terms don’t describe this directional uniformity. Grain lines refer to internal crystal features or growth patterns, not optical directionality. Habit is the typical external shape of the crystal, not its optical behavior. Macle describes a twinned crystal pattern, which is a structural feature rather than a statement about uniform optical properties.

When a crystal has the same physical and optical properties in every direction, it is isotropic. In optics, isotropic minerals are singly refractive, meaning light experiences only one refractive index regardless of the direction it travels through the crystal, so there is no double refraction. Diamond, with its cubic crystal system, is a classic example of an isotropic, singly refractive mineral.

The other terms don’t describe this directional uniformity. Grain lines refer to internal crystal features or growth patterns, not optical directionality. Habit is the typical external shape of the crystal, not its optical behavior. Macle describes a twinned crystal pattern, which is a structural feature rather than a statement about uniform optical properties.