What is the streak of the opal and tourmaline?

Opal typically has a white to light gray streak, though it can vary depending on the specific type of opal. Tourmaline, on the other hand, usually leaves a white streak, but its color can vary widely based on the specific variety and impurities present. Streak is determined by the color of the powdered mineral when rubbed against a streak plate. Both gemstones are primarily valued for their color and clarity rather than their streak.