LONDON.- A white diamond ring by Piaget is the star of Bonhams Fine Jewellery sale at New Bond Street on 30th April.

The marquise-cut diamond, weighing 8.97 carats, has been graded as D-colour - the top colour grade for white diamonds. At VVS2, it is also of excellent clarity. The diamond has been classified by the GIA - the world's premier diamond-grading laboratory - as Type IIa, meaning it is chemically pure. Diamonds of such high quality and large size are extremely rare and the present lot is offered with an estimate of £250,000-£350,000 (US$ 410,000 - 580,000).

Another top-quality diamond in the sale is a round brilliant-cut weighing 5.00 carats which has also been graded by the GIA as D colour, VVS2 clarity, Type IIa. It carries an estimate of £120,000-180,000 (US$ 200,000-$300,000).

A dazzling Fancy Yellow diamond weighing an astonishing 24.59 carats is another of the highlights. The step-cut diamond ring is offered with estimates of £150,000-£250,000 (US$ 250,000-$410,000).

Among the fine-quality coloured gems in Bonhams' sale is a Colombian emerald ring of exceptional colour, weighing 10.49 carats, which is estimated to sell for £150,000-£200,000 (US$250,000-$410,000).

A fabulous ring set with a cushion-shaped Burmese sapphire weighing 22.18 carats, mounted between two demi-lune-shaped diamonds, is offered with estimates of £175,000-£200,000 (US$290,000–330,000).

For connoisseurs of period jewellery the sale offers a chance to own a rare “Orange Tree” brooch made by Cartier Paris in 1914. This tiny jewel – one hundred years old – exemplifies early 20th century quality and innovation.