Oak apple due to the superficial resemblance and the preponderance of the oak marble gall in the wild. Other galls found on oak trees include the oak artichoke gall and the acorn cup gall, but each of these has its own distinctive form. Some common oak-apple-forming species are the "Biorhiza pallida" gall wasp in Europe, "Amphibolips confluenta" in eastern North America, and "Atrusca bella" in western North America. Oak apples may be brownish, yellowish, greenish, pinkish, or reddish. Oak galls have been used in the production of ink since at least the time of the Roman Empire. From the Middle Ages to
Royal Oak, Calgary Oak and Rocky Ridge. William D. Pratt School, a new middle school located near Royal Oak School, opened in 2016 serving students in grades 4-9 residing in Royal Oak and Rocky Ridge. It is named for Bill Pratt a longtime Calgary contracting general manager, who was chair of the Calgary Olympics, co-founder of the Canada Trail, and member of both the Olympic Order and the Order of Canada. Students in grades 10-12 from Royal Oak are served by Robert Thirsk High School in Arbour Lake, as well as St. Francis High School in Brentwood for students in the Catholic school