An 83 carat diamond is a rare stone, an immensely valuable stone, and probably one of a size that no human anyone knows would have a hand large enough to wear it.
You can browse the list, below, to find large stones and see their other physical measurements which are determined by each stone's cut
A 625 carat diamond would be a very large diamond, weighing 625 carats.
The two measurements you give are not related, essentially. The MM measurement could be the diameter of a brilliant cut diamond, or one measurement of another shape. The carat weight you give is a weight measurement of gemstones.
These gemstones weigh the same: one carat.
You can review the list, below, of named diamonds, none with the exact carat weight you describe, and documentation of the fact that a 99 carat diamond is not quite the world's largest.
The 'costliest diamond of the world' is measured by the price paid for a diamond. Depending on your particular criteria, there are several examples.When money changes hands to represent the costliest diamond...The JCK Marketplace Web site reports that an 84-carat [faceted] diamond sold for US $16.2 million, at "... $191,980 per carat, the highest price per carat ever paid for a white diamond at auction." This auction took place in 2007.At the same auction..."An extremely rare fancy vivid blue pear-shaped diamond, weighing 4.16 cts. and mounted as a ring, ...sold for $4.7 million. The per-carat price was more than $1.1 million, making it the second highest price per carat paid for a colored diamond at auction."In 2010, Reuters reported that "Petra sets record, sells diamond for $35 million" in its headline for the sale of a 507 carat raw diamond.
An 83 carat diamond is a very large diamond, and would command most any price you asked for it, depending on its colour, clarity and cut. Take your diamond to a certified gemologist who can help you document its characteristics, and potentially help you establish a market price for it.
One carat weight of diamond weighs .20 grammes, so your diamond is about half that weight, or roughly half a carat.
A 1.00 point diamond is one carat, so a .12 point diamond is a little over 1/10th of a carat.
A diamond is valued by its cut, clarity, carat weight and colour. A local jeweler can show you stones in this category.
A one carat diamond in the round brilliant shape measures aproximately 6.5mm at the girdle. If the diamond is another cut, measurements will be different.
You've given the carat weight of a diamond. 'Big', then, is based on the cut of the stone.
Carat is a weight, so its weight is one tenth of a carat or one tenth of .20 grams.
The diamond weighs .125 carats. Its mm measurements depend on the cut.
An eighth of a diamond carat, if it is a round cut, measures about 3.2mm at the girdle.
If the diamond is an ideal emerald cut with these measurements, the diamond may weigh about one quarter of a carat. Otherwise, you have stated the diamond's 'big' size in measurements.
Depending on the cut, a five carat diamond always weighs five carats. If the cut is round brilliant, the mm measurement at the girdle is about 11.
A forty-point diamond is nearly half a carat, which would be fifty points.