With experience, your ability to grade diamonds and evaluate their specifications will become second nature. Many dealers are very conservative in grading when buying, and become eager to over-grade when selling, to boost the profits. Being critical in grading a parcel of polished loose diamonds when buying, is essential in a profit-making business, but by the same token, if a buyer is too critical, a price will be very difficult to agree upon. The seller will lose interest in your business if you are consistently trying to under-grade his merchandise. On borderline grading calls, it may be necessary to make the purchase based on a lower grade unless you can afford to gamble, or perhaps there are other stones in the parcel that will make up for a losing or a break-even stone.