As far as we've seen though, natural diamond sales across the globe are very stable and values at middle-to-commercial tiers are still routinely standardized. Values at the top tiers (D-E-F with F-IF or VVS clarities above 10cts) are also doing very well at auction events. At the retail level though, the most in-demand sizes remain especially strong- 1ct, 1.5ct and 2ct weights.
Pictured below is 102.34 ct. round brilliant natural diamond, image credit: Sotheby's auctions. Rare and astounding gemstones like this are reserved for only those willing to pay the required fortune for owning such an opulent symbol of exclusivity and luxury. Large, high end natural diamonds have been increasing in value-demand quite steadily over the recent years, even with the advent of lab-grown stones.
Lab-grown diamonds are cheaper than natural earth-mined stones by around 40-60% at the wholesale / dealer level (sometimes 30% at retail), and *normal diamond testers (or moissanite testers) are NOT able to separate these from natural diamonds at all. Remember that their essential chemical composition is the same as a natural diamond's, so advanced spectrometry-based laboratory equipment would be required to positively identify most earth-mined natural diamonds from potentially man-made counterparts.
Nevertheless, we're currently aiding the screening efforts for several jewelry stores in order to make sure their diamond inventory is more accurately identified. (As a third-party evaluator though, we do not buy or sell diamond jewelry. We also do not recommend or discourage sale from any specific store or brand, in order to remain completely objective for all our evaluations.)
In the U.S., some stores are already selling lab-grown stones under the label- real diamonds, and while some may agree and others may disagree, they are following the definition based on same chemistry and cubic crystal structure. Essentially lab-grown diamonds are still chemically diamonds, they were just created in a factory lab.
Whether you're into lab-grown stones or not, it's best to be sure of what you have. These two kinds of diamonds have very different market values this 2019.
