Which garnet variety is often used as a substitute for diamonds due to its brilliance?

Rhodolite is the garnet variety that is known for its brilliance and has been used as a diamond substitute. Its vibrant purplish-red to raspberry color, along with its high dispersion leading to striking sparkle, makes it visually appealing and allows it to mimic some of the qualities associated with diamonds. The optical properties of rhodolite, including good clarity and a high refractive index, contribute to its ability to reflect light in a similar way to diamonds, enhancing its attractiveness for this purpose.

In contrast, other garnet varieties such as spessartine, almandine, and pyrope, while beautiful in their own right, do not possess the same level of brilliance or popular use as substitutes for diamonds. Each of these varieties has distinct characteristics, colors, and a different appeal, but they lack the combination of optical qualities that rhodolite exhibits, which allows it to stand out in this context.