Opal is a modern apple derived from Golden Delicious, and developed in the Czech Republic. It's other parent is Topaz, a well-respected variety also developed in the Czech Republic, which imparts a tart flavor to the sweet crispness of Golden Delicious. Visually it resembles Topaz, but with an attractive golden yellow flush from Golden Deliciuos which is particularly attractive.
Opal also inherits the good disease resistance of Topaz. Like Golden Delicious it grows best in warm dry regions.
Opal was introduced in the USA in 2010. It is a protected variety in both the European Union and USA. It is not related to the early-season English apple also known as Opal and developed in the 1930s.
Marketing information - OpalApple.com.