For centuries jade was thought to be a single gemstone, but in 1863 two different types were recognised: jadeite and nephrite, although differentiation between the two can be very difficult to the naked eye. Both stones are hard and tough and are suitable for use as ring stones, as beads and for intricate carvings. Jadeite occurs in a wide range of colours including lilac, white, pink, brown, red, blue, black, orange and yellow. The most prized variety, known as imperial jade is a rich emerald green. Nephrite ranges in colour from dark green to cream and has been carved by the Chinese for over 2000 years.