Opal was released in 2002 by Germany's Hüll breeding institute, one year after Saphir and part of the same general cluster of early-2000s German aroma-hop releases aimed at giving brewers a range of subtly different noble-adjacent options rather than a single fixed Hallertau character. Its parentage traces back through Hallertau breeding stock, though it sits at a somewhat higher alpha acid than either Saphir or true Mittelfrüh.
At 5.5-8.5% alpha acid, Opal is more genuinely usable for a moderate bittering charge than its lower-alpha German siblings, while retaining a mild spice and fruity aroma that keeps it in the same general noble-adjacent family as Hallertau Tradition or Perle. It doesn't carry a single dramatic distinguishing trait, functioning instead as a flexible, moderate-alpha German aroma hop. Opal's alpha sits comfortably between the very-low-alpha noble hops like Saphir and the considerably higher-alpha American varieties covered elsewhere on this site — the IBU calculator will show exactly where an Opal-based charge lands between the two. Hallertau Tradition is the closer substitute given a similar alpha range and general character, while Perle offers an alternative with its own minty edge if that's an acceptable trade. German lager and traditional ale styles use Opal wherever a dependable, moderate-alpha German hop is needed without a single dramatic aroma trait to build a recipe around. Opal's alpha floor (5.5%) sits exactly at the ceiling both Spalt Spalter and Tettnanger reach rather than above it — all three touch at that number — but Opal's own ceiling runs to 8.5%, well past either, making it the more genuinely usable of the three for an actual bittering charge rather than a purely late addition.