hi i teach faceting to new bee’s and have been since the 70’s. having worked for/at crystalite from 68-77 making the flat laps and demo’ing them at shows i find still many of them i made back then are working good. i have also found that the china made are VERY good as they don’t skimp on the diamond. in some cases they over do it and you have to work hard to break them in, but they are the best buy and cheapest. we here use both 6″ and 8″ and i find the 6″ is good for beginners, as, if they have an accident and lap is damaged no real loss they are cheaply replaced. we use what ever coarse to get basic faceting started and formed, then go to 1200 and finalize meets and cutting. like i said we go to tin at very slow speed with water drip about one drop every 30 sec. just enough to make a muddy slur, applying diamond powder near center spindle and work out to center work area, your stone will work the dampened diamond into the lap as you polish and water drip as close to center spindle as possible. the one thing you have to be careful about it the quality of the diamond powder, i’ve bought from many sources and only found one with real quality. for cabbing i bought a syringe of 50k compound from a supplier in So. CA. and it was totally bad and caused scratches. some powders are the same. diamond does polish everything even other diamonds. the thin plastic type polishers do compress distorting the facet.