Out of curiosity is there a place to buy a large synthesized Diamond to be used as paperweight? I though that would be cool and since I don't need it to be cut the price should be pretty reasonable.
Synthetic diamonds are not that cheap (about 50% of the price of the natural ones), because they are not that easy to make. The large synthetic diamonds are grown in HPHT medium (>2600 degrees C), and even if they are made by a machine, they still grow at an incredibly slow rate (maybe one micron/hour), so you have to keep a huge temperature and pressure for months to get a big one - and maybe at the end it shatters and you just get 3 carat diamonds from it. So the costs are not really paperweight-ready (or maybe you have a few millions to spare for a paperweight).
The biggest synthetic diamond data I could find is 60-carat[1] unpolished (10 carat polished).
Diamonds are also not really good as a paperweight (one carat is 0.2 grams, a sheet of A4 paper is heavier than a 25-carat diamond).
Large cubic zirconia jewels are available.[1] This one is 45mm across. Another supplier offers up to 200mm diameter, but that may be a special order item.
It really depends on how loose your classification of "diamond" is and how large you want. Cubic zirconia is quite popular with hobbyist and some professional faceters and is quite readily available in a range of colours (try searching for cubic zirconia rough) but it's more difficult to manufacture the larger you get. Moissanite is much closer to natural diamond in both hardness and refractive index but it still seems to be fairly inexpensive uncut. Not too familiar with other diamond synthetics but the range seems to be growing.
