Europium is one of the rarest of the rare earth elements on Earth. It is one of the rarest and most critically endangered lemurs. The Hainan black crested gibbon is among the rarest and most endangered apes. Wolverines are one of the rarest and most elusive mammals in North America. It is one of the rarest and most valuable precious metals. It is considered among the rarest of all gemstones. This species is one of the rarest in the world. The 1804 dollar is one of the rarest and most famous coins in the world. The lion-tailed macaque ranks among the rarest and most threatened primates. Protactinium is one of the rarest and most expensive naturally occurring elements. Green is fairly scarce but blue and white are the rarest. Perfectly round pearls are the rarest and most valuable shape. The Orinoco crocodile is one of the rarest reptiles in the world. By the late 1980s, these discs were among the rarest and most valuable Beatles collectibles. Western Ghats of India has of the rarest and unique collections of flora and fauna.