Zircon is a square mineral whose name is derived from the Persian "zargun" - colored like gold, according to the color of one of the varieties. Zircon is the oldest known mineral on Earth (in relation to the age of the Earth, not to human knowledge), the age of the sample found in Jack Hills in Australia has been estimated at 4.4 billion years. The hardness on the Mohs scale is 7.5. Known varieties of zircon include: "hyacinth" (yellow-red, red-brown), "jargon" (colorless, pale straw yellow on Sri Lanka), "starlit" (blue, found in Pailin, Cambodia). It most often occurs in the form of tabular to prismatic crystals, with a square cross-section, terminated by a quadrilateral pyramid, up to 30 cm in size. Also in the form of irregular grains, massive.