Diamonds, diamonds, diamonds. There has been so much information and misinformation available over the years and it only seems to have grown exponentially with the growth of the Internet. There are so many different topics to discuss when talking about diamonds that it's hard to know even where to begin.
So let's start with a little history. Diamonds have been known almost since man became civilized (assuming you can say that man is actually civilized even today). But when diamonds were found in ancient times they were extremely hard for the people to cut or polish, what with their hardness and all and no modern technology to help. Some of the oldest known historical diamonds were simply polished with a few facets on the top and left flat on the bottom. It was about the best that could be done at the time.
However, over time, man, in his never ending quest for wealth finally figured out how to take such a rare (at that time) substance and actually cut it into something that sparkled a bit, particularly in candlelight. Most diamond crystals occur in the form of two inverted pyramids and early cutters figured out that they could lop off a piece on the top, and then add some facets around the still somewhat square stone to get some nice light reflection. These early cuts are known as "old mine cuts", almost always have a squared off outline, high crowns (tops) and either excessively shallow or deep pavilions (bottoms). Their facets were almost always lopsided, poorly placed and there were often naturals around the girdles (a natural is a part of the original diamond crystal skin that was never polished---you see this on some modern cuts as well because in a cutters' efforts to retain as much weight as possible they would often not even finish rounding up a diamond's girdle on the narrower spots on the crystal).
In the early 20th century, cutting techniques improved and they figured out how to actually round off the outlines of the crystals, achieving round stones. They also began to realize that if they didn't leave such a large crown on the stone they could actually cut a second stone from the same crystal. These early stones, which are still usually top heavy, have very small tables, are not very well cut either, but have rounded outlines are known as old European cuts.
Then in 1919, a diamond cutter/mathematician who's name was Tolkowsky worked out a formula for what angles to cut a diamond to in order to maximize the brilliance and light reflection from the crystal. This cut became known as the American Ideal Cut and was the standard against which all round cut diamonds were judged until just fairly recently. Tolkowsky had a cousin/apprentice who's name was Lazare Kaplan. Lazare Kaplan was the first person to adopt and popularize the American Ideal Cut and has continued to cut it ever since. The company Lazare Kaplan is now known as Lazare Diamond and they were the first in a number of other important advancements in the diamond industry, including developing the first lasers that could be used to imprint numbers (or words) on the girdle of a diamond (I believe they still own the patent) and a new high pressure high temperature treatment used to change the appearance of certain types of diamonds (not marketed under their own name).
Daniel R. Spirer Jewelers has been selling Lazare Diamonds for close to twenty years. The best thing about them is that every stone they sell will absolutely be an ideal cut diamond. Unfortunately a lot of people today sell stones they claim are ideal but often they are just better cut than some other stones and they don't actually have the proper angling on the facets or the correct table size to actually be called ideal. In my book it's a little like being pregnant. You can't be almost pregnant and you can't be almost ideal. The stone either meets the criteria or it doesn't.
I don't want to overwhelm you all with information at one time so I'll leave this here. Next posting, I'll talk a little about quality and rarity of diamonds.