If gemstones are grown in labs in conditions that mimic nature, i.e., not always perfect, then the resulting crystals will have variations in them when it comes to color and clarity, resulting in the lab-grown versions being unique. Now, some crystals and gems are much easier to grow with some methods over others. One method may yield crystals of uniform color and flawless clarity, while another will result in each gemstone cut from the rough being unique.
For simulants like CZ, the process is pretty easy for growing the crystals and give fairly uniform results.
Moissanite is much easier to grow than the Amora Gem, (they need different environments in order to obtain the different crystal structures), but each batch of rough will be *slightly* different from another, so while the individual stones can be decently uniform, the slight variations still result in a unique stone. I believe the “base” clarity for both moissanite and amora gem is “VS”, with the AG varrying anywhere from IF to SI as of now.
Now, lab grown diamonds are notoriously difficult to grow, with yellow diamonds being the easist, white being much more difficult. If the technology to grow large, colorless, flawless diamonds reliably was around, I’m sure many of us would be rocking them!
Both Gemesis and D.NEA Diamonds offer lab grown diamonds, and the web sites are a lot of fun to check out, I plan on purchasing a lab grown blue diamond for a pendant. 😀
Edit: As for stats, the color of sims, diamonds, and moissy can be graded on the D-Z scale, clarity can be graded the same, and whether hand cut or by machine, each stone will still have its own unique measurements, even if there are a significant number that are quite similar. So, I own a J colored 7.73×7.68mm Amora-ized OEC moissanite with VS clarity.