Approximately between $400-$500
Blue Diamond
You can complete your own research by visiting a Canadian jeweler that was in business in 1900, and exploring the records associated with the sale of any blue diamond.
The Engagement Ring was created in 1991.
If your talking about the engagement ring in miscellania and etceteria you just get a normal ring there is no special engagement ring or anything like that
If someone is looking to buy their future wife a blue diamond engagement ring, the best place to look is a reputable jewelry store. Most high end jewelry stores should have blue diamonds in stock, but if there are none available to look at in store, they may have a brochure or could order one.
About $800
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.
A 4 carat diamond ring would be ridiculously expensive. In the $100K mark I would expect. If someone is showing you their 4 carat engagement ring, it is probably cubic zirconia.
If you plan to ask her to marry you, you should give her an engagement ring. The majority of engagement rings are diamond but keep in mind that you can easily find a diamond engagement ring for your budget. If you buy a nice engagement ring, you and your bride-to-be can buy your wedding rings with or without diamonds or just plain gold (or another material) wedding bands.
Black diamonds are a rare form and can be found in the African Republic and parts of Brazil. The cost of a black diamond engagement ring can differ depending on cut, style, and other stone settings. Front Jewelers sells black diamond engagement rings starting at approximately $1500.
The value of a diamond depends on its cut, colour, carat weight and its clarity. A local jeweler can answer your question. A 12.5 carat ring has to be cubic zirconia. Such a high caratage is preposterous for a diamond engagement ring.
Blue Nile has a page on their website that teaches you what to look for when shopping for a diamond engagement ring. They also show all of the different cuts of diamond so that you will know which style you like best before shopping.