Sardonyx is the same stone as onyx, a banded agate with regular and uniform stripes. Onyx has a black base, sardonyx has a brown base. Like most agates, sardonyx and onyx are often dyed for color enhancement and uniformity.
Tigereye is a banded golden brown quartz with an appealing golden luster. One can't help but think of a sun soaked tiger when viewing this versatile stone. The yellow and brown stripes of this stone appear to swap colors when viewed form different angles.