“Halley’s Comet”, is recorded in the Guinness Book of Records as the world’s largest uncut black opal. The massive stone was found by a group of opal miners on the Leaning Tree Claim at Lightning Ridge known as “The Lunatic Hill Syndicate” about the time “Halley’s Comet” appeared in Australian skies. This Opal comes from the 3-mile Black Opal feel of lightning Ridge Australia” known as the best quality Black Opal gemstones internationally. It weighs 1982.5 carats and measures 100 x 66 x 63 mm, or 4 x 2-5/8 x 2-1/2 in.
Halley’s Comet was for sale in 2005 for AUD$1.2 million which is USD$854,400. The gem has a thick gem quality green and green/orange color bar and is the largest gem to be found at Lightning Ridge to date. It is the third largest gem grade black opal ever recorded, the largest one extant, and the largest specimen ever found in its region. The Halley’s Comet Opal is a very fine specimen, with few flaws or blemishes and a large green and orange 1.6 cm (0.63 in) thick color bar which goes through the opal.