All else being equal: carat weight, cut, and clarity, a blue diamond will always be more expensive than a white diamond.
Stone for stone, a diamond is more expensive than an emerald.
Platinum is not more expensive than a beautiful, natural diamond.
Mined or natural diamonds are more expensive than man-made diamonds. If monetary value is an advantage, then a mined diamond has the advantage of value.
Gram for gram, a gem-quality diamond is always more expensive than platinum. However, gram for gram, platinum is always more expensive that industrial diamonds. It is important to keep in mind that diamond prices are kept artificially high because DeBeers hides away much of the diamonds they mine to exaggerate scarcity i.e. diamonds are a manipulated market (vs. a free market).
At a first glance, this seems really weird since:oxygen is essential for human survivaldiamond is not essential for human survival...and therefore, oxygen should be expensive whereas diamond not.However, looking at the scarcity we realize that there are a lot more oxygen than there are diamonds.Therefore, since oxygen is abundant (while not infinite), it is cheap (unit price). and since diamond is extremely scarce, it is expensive.
All else being equal: carat weight, cut, and clarity, a red diamond will always be more expensive than a white diamond.
blue
A natural blue diamond will always be worth more than a white or colourless diamond, given equal carat weight, clarity, and excellence of the cut.
Stone for stone, a diamond is more expensive than an emerald.
Every diamond is valued by its clarity, colour, carat weight and cut. Compared on an equal basis, you will pay less for a black diamond.
it will glow white, or more than likely, blue
Platinum is not more expensive than a beautiful, natural diamond.
Given the same carat weight, clarity and cut, you will pay more for a pink diamond than for a 'white' or colourless diamond.
By weight, when comparing equal amounts of platinum and diamond, gem-quality diamond will always be more expensive.
There are "yellow", "blue", white", "pink", and even "orange" diamonds, but it refers to a faint "cast" the color of the diamond has due to slight impurities in it - the diamond still appears overall to be "white".Another AnswerOther than 'white' diamonds, graded D colour to Y, there are coloured diamonds with shades of colour, from faint, to very light to light. The grade of a coloured diamond depends on the amount of mineral included in the diamond which gives it colour. For example, boron gives diamond a blue cast.A blue diamond can be graded Faint Blue, very Light Blue or Light Blue grade. Blue is one of the rarest colours of natural diamond.(There are also vivid grades, fancy grades and fancy vivid grades of coloured diamonds.)You can read more about grading coloured stones, below.
A red diamond will cost you more than a blue diamond, given that all other characteristics of the stones are equal.
Your question assumes that a diamond has changed hands for money. Many important diamonds, however, have never been sold, but have been owned based on the stone being a spoil of war or a gift to royalty.The 'most expensive diamond' may be in regal crown jewels owned by a nation state. The British and Thai crown jewels are examples of magnificent diamonds held this way. Because they have not changed hands for money, there are essentially and otherwise priceless.There are, however, a few examples of expensive diamonds, some with their record per-carat prices:The world's most expensive diamond -- 35.56 carat Whittlesbach blue -- sold for $24.3 million, beating a previous record of $16.5 million for a 100-carat diamond in 1995.The DeBeers Millennium Star DiamondThe Taylor-Burton DiamondThe CentenaryCullinan (never sold, gifted to the British Crown)Hope DiamondA 7.03 blue diamond sold for £6m ($9.5 million) in March 2009 in Geneva.Chopard blue diamond ring for 16,260,000 dollars. It has a 9-carat blue diamond, more white diamonds, and a 18k white gold setting. (In general, blue diamonds are the among rarest and most expensive diamonds in the world.)