A diamond of this size is uncommon. From your comments, the purity of the gold is also uncommon -- soft, indeed, for a diamond of this weight.
Best practices dictate that you take your ring to a certified gemologist who will document the ring and give you an estimated market value. Expect to pay for the certificate.
You can read, below, about a 32.72 carat diamond, with an auction estimate of US$1,400,000 to US$1,800,000.
45.52 CaratsThe Hope Diamond is 45.52 carats. By comparison the average engagement ring is only 0.3 carats.
The largest carat diamond ever is the Cullinan Diamond. This diamond weights in at 3106.75 carats which is around 1.37 pounds. The biggest diamond ring however, is 150 carats.
You can buy a diamond about 13 carats from Blue Nile today and spend between US$535,000 and US$1,763,000. Then you'd pay for the metal setting for this stone.
$60
The weight of the diamond -- if it's a round cut diamond -- can be about 1.25 carats. The carat weight of the ring depends on the metal and that weight will be described in ounces, not carats. You can pay a certified gemologist to give you the exact weight of the diamond and its metal ring setting.
A 60-point diamond weighs just over half a carat (.50 carats). The size of the ring is not related to the weight of the diamond.
The information you give can be answered this way: with 96 diamonds each weighing .03 carats, the total diamond weight is .03 x 96 or 2.88 carats.
The metal has a karat value, meaning that it's gold; the diamond weight is measured in carats. Since the diamond stone and the metal ring are separable, anything stamped in the metal usually refers to the metal and not to the stone mounted therein.
What you have to sell is worth whatever someone will pay you for it. In October 2012, there were diamonds of about this weight sold at the Christie's sale. You can read more about the sales, below. In particular a diamond weighing just over 50 carats sold for US$9,500,000. In a ring, the mounting would be an additional cost.
Every diamond is valued by its cut, clarity, colour and carat weight, which together with the price of the metal in the ring would total the cost of a ring -- regardless of the year.
Since 40 carats is large for a diamond, you can watch auction houses to find an auction for such a diamond.As an example, The Emperor Maximilian Diamond sold at Christies in 2010 for US$1,762,500. Its documentation included this:"[Report] from January 2010 from the Gemological Institute of America stating that the diamond is I color, VS1 clarity, with very strong blue fluorescence... accompanied by a supplemental letter dated 23 February 2010 from the Gemological Institute of America attesting to the re-cutting of the Emperor Maximilian Diamond from 41.94 carats to its present weight of 39.55 carats ."
Cubic zirconia rings are much less expensive than diamond rings. A cubic zirconia ring may cost around $700 while a diamond ring can cost upwards of $40,000. Cubic zirconia is a much less valuable stone than diamond is and cubic zirconia rings are priced as such.