I didn’t see this earlier, or I would have responded sooner. While I am on this forum to learn about jewelry making, most of my hands on experience is in faceting, buying and selling colored stones. I am also a '96 grad of the GIA gemology course, so I, too, understand colored stones and something about the colored stone marketplace. The fact that your friend has a comprehensive inventory, hopefully with gemstone weights, dimensions, descriptions and photos of everything is very helpful in selling. However, trying to sell an extensive collection all together pretty much guarantees that you will get a price well below wholesale value, unless some atypical collector comes along who just falls in love with it all…and that would involve waiting for the right person to show up…and they might not, ever. Meanwhile, the longer the collection sits around on the market, the less potential buyers will offer. Jewelers are not going to buy a collection which doesn’t meet their immediate sales needs when they can get what they want thru their usual suppliers at typical wholesale, so they are going to want to pay less, maybe much less. The very expensive stuff, the very cheap stuff and the very unusual or out of fashion stuff is going to sit around, so the price is going to be computed basically on what the jeweler can set and sell readily. Unless your friend was very savvy and bought in parcels or from close to the source, they bought at retail and are selling at wholesale, and, with the lot sale, at less than wholesale. Because this is an old collection, the owner may not be upset, because it may have appreciated in value even if sold at 50% to 75% of wholesale. However, the proper question to ask is what the value was when bought and then add the time value of the money spent. In other words, if you’d put that money in the stock market, what would you have now? And as a rule of thumb (rule of 72) your money historically doubles in the stock market (index funds) about every 7 or 8 years.
All that said, there are collectors, speculators and auction houses that would buy a whole collection. Speculators and auction houses would then sell individual pieces or lots for wholesale prices or better or even hawk the stones on Tiktok or Instagram, where there is some retail trade in loose gems by people who know they can buy good stones and have a jeweler set them a lot cheaper than they can buy jewelry out of a store. So your friend should contact some of the better auction houses, who all have gemologist-appraisers on staff. However, I would approach the auction houses proposing they act as seller’s agents. They will ask that you ship the collection to them and then they will decide what they will auction. They photograph and describe each piece or lot and auction it off, sometimes with a reserve if you and they agree that that is best. They take a hefty cut of the proceeds (1/3 to 1/2?), but the prices are auction prices, which are sometimes higher and sometimes lower than jeweler wholesale. However, for good items, the auction house would want a reserve so that they could offer the item at another sale which might have a better climate for the item if bidding goes dead.
The best prices would probably be had if you could employ a gemologist to value the stones and sell them for you. Same deal as the auction house, but, because you’re dealing with an individual, the overhead and their cut would probably be lower.This is the kind of work I would like to add to my business selling cut stones, but your friend’s collection is not in the US and is far too extensive for me to undertake, esp. at present, when I’m focused on developing a market for my own cut stones and those of some collaborators.
Lastly, I would say that just having an inventory doesn’t establish a value with colored stones. You have to know pretty exactly the color compared to the ideal for that species, the inclusions, if any (and if you look close enough, they are there, and sometimes that is helpful, because it proves natural vs synthetic), the cut type and level or workmanship, the light return and the stone’s diaphaneity (transparency) as well as any color zoning and probable/possible treatments. Your friend might want to invest in a valuation program or a gemstone guide with color comparison reference and price guide. It’s possible that you could guide him to knowing more about the prices, which is helpful if they do decide they want to get the most out of the stones they have. Such would run about $400 to $650 for the reference material and a year of price lists.
Hope some of this is helpful. If I’ve gotten some of this wrong, let me know, I’m always interested in learning more. -royjohn