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

• A. Singly Refractive (Isotropic)
• B. Specific Gravity
• C. Habit
• D. Macle

Answer: (A)

Isotropy means having the same physical or optical properties in all directions. In optics, an isotropic material shows a single refractive index no matter which way light travels, so it does not exhibit double refraction. In gemology, this is described as singly refractive or isotropic because light isn’t split into two rays. That’s why this term is the best fit: it directly describes uniform properties in every crystal direction. The other terms don’t address directional properties: specific gravity is about density, habit is crystal form, and macle refers to a growth or fracture pattern.