A diamond of this size with this provenance would only be sold at an auction -- unless it was sold at a private sale.
Its pre-sale auction estimate would be in the multiple millions of dollars US. It's last sale fetched US5,000,000 in 1979, and it was sold again -- privately -- for an undisclosed sum.
You can read more below, about large diamond auction prices.
250 carat Diamond- uncertain amount as can be auctioned; very few diamonds of this size25 carat Diamond- $1 million to $2 million; for a lower quality stone2.5 carat Diamond - $5,000~$8,000Another AnswerYou can buy a 2.5 carat diamond today on Blue Nile and spend from US$12,000 to US$16,000.Also, a 15 carat diamond is available on Blue Nile today for just over US1,000,000.
Today on Blue Nile, you can purchase a one carat SI1 diamond and pay about US$4,759; and a one carat VVS1 diamond and pay about US$12,252.
Every diamond is valued by its clarity, colour, carat weight and cut.
What you have is worth whatever someone will pay you for it. If you mean .01 carat of a diamond, then its value is lower than if you mean 1.00 carat diamond. The lowest price today on Blue Nile for a 1.00 carat diamond is US$2,151. The lowest carat weight you can purchase there weighs .24 carats.
A diamond of about that carat weight can be bought today on Blue Nile, and you'd pay between US$5,732 and US$23,606, depending on the exact carat weight, cut, clarity and colour that you want.
Today, on Blue Nile, you can buy a diamond of about this carat weight and pay between US$509,719 and US$1,376,169, depending on the colour, clarity, cut and exact carat weight that you want.
A diamond is 'worth' whatever someone will pay you for it, in whichever currency is being used for the transaction. The smallest diamond available for this kind of comparative purchase today, online is a .25 carat diamond, larger than your .10 carat query. You can buy this diamond today 11Sept26 on Blue Nile and pay between US$232 or 139.50 BPS and US$516 or 332.52 BPS, depending on the cut, clarity, colour and carat weight of the diamond.
You can purchase a diamond of this carat weight today at Blue Nile and spend between US$9,701 and US$27,984, depending on the colour and clarity that you want.
You can buy a 6.01 carat Flawless diamond today on Blue Nile, with an F colour and pay just over US$423,000.
Any diamond is worth whatever someone will pay you for it. Today, on Blue Nile, you can purchase a diamond of this carat weight and pay between US$4,249 and US$39,069, depending on the cut, colour, clarity and exact carat weight that you want.
Any diamond is worth what someone will pay you for it. You can purchase a marquis diamond of this carat weight -- half a carat -- today on Blue Nile and spend between US$516 and US$2,935, depending on the clarity and colour that you want.
Any diamond is worth whatever someone will pay you for it. Today, on Blue Nile, you can purchase a diamond of this approximate carat weight and pay between US$1,508 and US$4,981, depending on the cut, colour, clarity and exact carat weight that you want.