The answer assumes you mean a ~25.00 carat stone and not a .25 carat stone.
Today's search for loose diamonds produced this result:
A round stone of 27.12 carats, with a J colour, I1, without a certificate and graded as 'excellent' cut. It is priced at US$576,249.00.
There is no standard price per gram/ ounce or carat for diamond, since a diamond is valued by its cut, colour, clarity and weight (carat).
The price of a 1-carat diamond can vary widely depending on several factors, including the diamond's cut, color, clarity, and carat weight.
A 25 carat diamond will be difficult to find, since that size of stone is larger than most diamond merchants have on hand. For comparison, however, the link below shows the auction price of a 35+ carat stone, which sold for over US$24 million.
Your price for any diamond depends on the cut, carat weight, colour and clarity of the diamond that you want to buy.
The price of any diamond depends not only on its carat weight, but on its colour, clarity and cut. A local jeweler can show you a diamond of this carat weight and give you a price, depending on its other characteristics.
A .25 carat round GIA certified diamond in F color and VVS2 clarity costs about $590 and a .25 carat princess diamond in E color and VVS1 clarity costs $510.
A diamond's value is based on its carat weight, its cut, its clarity and its colour. A local jeweler may be able to answer your question given an individual stone.
The value of a diamond depends on its cut, its clarity, its colour and its carat weight. A local jeweler can give you the answer you want.
The value of a diamond depends on its cut, its clarity, its colour and its carat weight.
The price for a one carat diamond cluster will vary greatly depending on things such as the quality and size of the diamonds in the cluster. The type of ring setting is also a factor in price such as 10, 14, 18 or 24 carat gold. An example is a 10k white gold diamond cluster is $600 at Zales but a 14 carat diamond cluster on the Ross Simons site sells for $2,471.
1.50 dollars
Black diamonds can be estimated approx. $10,000 per carat.