Because diamonds are graded using several complex measures, and because they’re so expensive, the business attracts lots of scammers and shady salespeople. Here are tips for getting a smooth sale.

Getting Good Advice

Educate yourself. The best way to protect yourself from a dishonest diamond dealer is to demonstrate you know what you’re doing. Our review of how diamonds are graded and priced, and our tips on what you should (and shouldn’t) care about, is a good start. The customer reviews of jewelry stores here at Checkbook.org will also help you find helpful, trustworthy retailers. The best jewelers provide low-pressure environments and give customers value-centric crash courses in diamonds. A good store should also let you inspect and compare numerous stones and offer customizable settings. Feeling pressure or having difficulty getting a firm price quote? Walk away.

Beware of Scammers

If you’re shopping for a large diamond, tell retailers you’ll consider only gems with full GIA reports. If the store can tell you only that a diamond is “certified,” without a designation from the GIA or other reputable organization, ask to see something else. Generic certifications tell you nothing about stone quality.

Prepare for a Wait

Getting a good diamond, like the love it represents, takes time. It takes a few days or weeks for loose stones to ship to the store. If you pick a custom setting, or order around holidays, you’ll wait even longer.

Compare Loose Stones

Because some stores pre-set lousy diamonds to hide flaws, tell retailers you’re shopping for a loose stone or stones. Focus on setting-and-design decisions second.

If a store shows you just one stone, that’s a red flag. The more diamonds a seller can trot out the better. But be wary of retailers that start by asking you to compare very dark stones with very light ones, or to judge well-cut gems against poorly cut ones. These comparisons are often intentionally simplistic and done to push customers into paying too much for clearly superior stones.

Instead, ask to compare at least a half dozen stones of similar cut, weight, color grade, and clarity. Review each stone’s GIA report; determine whether or not defects and differences are visible, and whether the differences matter to you. The more stones you examine the more comfortable you’ll get at discerning good-looking diamonds from bad ones.

As you compare, focus on value, thinking about whether or not you care about very small or even indistinguishable differences. You’ll get a lot more bang for your extra bucks by buying an excellent-cut diamond. But if you can’t otherwise discern differences in quality between two stones, don’t pay more for the higher-quality stone. Most shoppers should avoid paying extra for diamonds with color grades above F or with clarity scores better than SI1. And avoid stones that weigh in at popular or round-number carat cutoffs.

Shop for Price

We report here the range of prices quoted to Checkbook’s undercover shoppers when they contacted a sample of Boston area stores and online retailers to collect their prices for loose diamonds they would offer that fell within the following narrow parameters:

• Mined Diamond, Stone A—Excellent cut, 1.50–1.55 carats, VS1 or VS2, G or H color, no fluorescence, GIA certified
• Mined Diamond, Stone B—Excellent cut, 1.00–1.05 carats, VS1 or VS2, E or F color, no fluorescence, GIA certified
• Lab-Grown Diamond, Stone A—Excellent cut, 1.50–1.55 carats, VS1 or VS2, G or H color, no fluorescence, GIA or IGI certified
• Lab-Grown Diamond, Stone B—Excellent cut, 1.00–1.05 carats, VS1 or VS2, E or F color, no fluorescence, GIA or IGI certified

When collecting prices for products, we prefer to compare identical items. But that’s usually not possible to do with diamonds. Even for a narrow set of parameters, you’ll find there are hundreds of diamonds on the market, and if you compare using GIA identification numbers you’ll find that stores seldom offer the exact same item. If you specify diamonds using similar criteria that we used, you’ll find that some stores will offer only one or two choices, but many will offer at least a handful of options, and the websites of large jewelry store chains and online-only sellers will have hundreds in inventory. (For our price survey, we collected prices from the large chains’ websites, where available.)

But having many choices actually works in your favor by giving you the chance to make a value play. Remember, among similarly graded and sized stones, differences that are imperceptible can still have a big impact on price. You’ll want the opportunity to select from lower-priced stones that will—at least in your judgment—do just as well as higher-priced options.

For retailers that quoted a range of prices to our shoppers, we report the lowest, median, and highest prices we received. For our set of parameters, some stores offered choices that represented huge ranges of prices. For example, for the smaller mined diamond we sought, online seller Rare Carat offered 1,442 different stones priced from $7,110 to $12,848, with a median price of $9,600.

You can see that the local stores our undercover shoppers surveyed quoted dramatically different ranges of prices for our very similar sample diamonds. For the larger mined stone, DePrisco Jewelers offered a median price of $11,500 and Khan Diamonds’ median price was $12,800, compared to median prices of more than $18,000 from Helzberg Diamonds, The Jewelry Exchange, Keegan’s Norwood Jewelers, and Tiffany.

Prices available from some—but definitely not all—online-only sellers were lower than those offered by most local retailers. Among online-only sellers, Ritani offered the lowest overall prices for mined diamonds and VRAI and Ritani offered the lowest overall prices for lab-grown. Click here for advice on buying diamonds online.

We also checked prices at Amazon and Costco. Both offer diamond jewelry (Costco’s selection is very limited). Our shoppers found Amazon’s jewelry section and filters incredibly difficult to navigate. After hours of searching we were able to identify only a few offers from Amazon’s Marketplace sellers for lab-grown stones that met our specifications, but we found no jewelry with mined stones that met our parameters. And we often found its sellers’ listings lacked specifics about certification and other important matters.

At Costco’s website we found a ring with a stone that met most of the specs for our smaller mined stone. Unfortunately, Costco doesn’t provide information on cut quality.

Sometimes our shoppers could use supplied GIA numbers to see that the exact same stone was offered by multiple stores. In these instances, we still found sizeable price variations.

The message is clear: Shop around. Figure out what you want to buy. Decide on shape and on a narrow range that you’ll accept for carat, cut, color, and clarity. For example, you might decide to shop for an excellent-cut round brilliant weighing 1.6 to 1.65 carats, with color grade between G and H and VS1 or VS2 clarity. Then get pricing from several stores for diamonds they can supply that meet your specs. When you ask for prices, let each store know you’re contacting several retailers. Doing so will prompt most stores to offer their lowest prices and eliminates awkward negotiations.

Ask for GIA numbers and then look up each of the stones offered at GIA.edu. Use those reports and the info provided in this article to make your final choice.

Also Shop Around for Lab-Grown Diamonds

As we discuss here, lab-grown diamonds are identical to mined ones—even expert jewelers can’t tell them apart without submitting them to a lab for analysis. But you’ll definitely notice cost differences between the two: We found you can save thousands of dollars by buying lab-grown diamonds—our 1.5-carat lab-grown option cost about $10,000 less than its mined twins.

Like mined stones, we found big price differences for manufactured stones among retailers selling them. For example, VRAI’s median price for our 1.5-carat diamond was $2,694; MiaDonna’s median price for a nearly identical lab-grown stone was $4,360.

Beware of Trends

Unless you’re a ginormously rich celeb, a diamond is, if not forever, hopefully a very long-term commitment. On your 20th anniversary, you might not want to look down at a ring design or diamond cut that’s the leisure suit or pillbox hat of the jewelry world. While you can always re-set an out-of-fashion ring, that’ll cost you, and most of us would rather form sentimental bonds with designs that endure.

Consider Less-Expensive Gems

Sapphires, rubies, and other stones offer similar dazzle at significantly lower prices.

Consider Clusters

If you want a lot of diamond for not a lot of dollars, consider buying a ring designed with a cluster of small diamonds. It will cost far less than a comparable-size single stone, and no one will notice the difference unless they get close.

Review the Return Policy

Buy from stores that offer returns with a full refund within 30 days. But if you purchase a custom setting, know you’ll likely pay for design and fabrication costs.

Pay by Credit Card

If a store doesn’t come through, you’ll have the option of disputing a credit card charge under the federal Fair Credit Billing Act and the consumer-friendly policies of the credit card companies.

Avoid High Interest Rates

Although chain and department store salespeople might offer steep discounts for signing up for a new credit card to pay for your purchase, these cards (and offers that let you defer payments for months) usually impose high interest rates.

Get an Appraisal

After purchasing an expensive diamond, take the stone to an independent appraiser. Although you’ll have to pay about $50 to $200 for the appraisal, it’s good insurance against being given—either intentionally or by mistake—a switched-out gem that’s of lower quality than what you paid for.

Don’t go to an appraiser recommended by the store. You can find reviews of appraisers here at Checkbook.org. The GIA also lists appraisal associations at gia.edu/library-appraisal-associations.

When getting appraisals for jewelry, don’t expect the retail and appraisal values to match; the appraisal figure will usually be much higher. If the jeweler provides or arranges for the appraisal, this phenomenon is often a byproduct of the jeweler trying to make a customer feel like they have just received a good deal.

Also, the purpose of an appraisal is to estimate the replacement cost for insurance purposes in case the item is lost or stolen. To save money on insurance premiums, there is no need to insure a diamond for more than what you paid.

The resale value for diamonds, on the other hand, is much lower than retail. You would be lucky to sell your diamond for half of what you paid for it, due to low demand for “used” diamonds and a limited marketplace (retailers, wholesalers, pawn shops, or directly to another consumer). Several online gold- and diamond-buying websites have popped up in recent years, easing the resale process. Nevertheless, a diamond isn’t a good financial investment.