According to the Guinness Book of World records, the largest uncut black opal in the world is the Halley’s Comet Opal.
Halley’s Comet is a “short term” comet, which orbits the earth in a period of about 75 years. One of those years in which it was visible was 1985, and that’s when this opal was found, by the Lunatic Hill Mining Syndicate. (Halley’s Comet will return again in 2061.)
It is the third largest gem grade black opal ever recorded, the largest specimen ever found in its region — Lightning Ridge, and the largest one still extant.
It weighs 1,982.5 carats and is about the size of a man’s fist. It is a very fine specimen, with few flaws. A large green and orange color bar goes through the opal.
Formed about 20 million years ago, it is an example of a nobby, a natural lump-shaped opal found only at Lightning Ridge.
Halley’s Comet Opal sold for a record price, $300,000, in 1995.