Why Two Gemstones of Identical Carat Weight Command Radically Different Prices

There are many different gemstones, to the point where, if you take two gemstones that each weigh two carats and put them under similar light, they will be radically different?  For examples of blue beryl, browse the aquamarine gemstone collection.

Even if they're the same blue, the same oval cut, and weigh the same, knowledgeable gemstone traders will see a price difference of thousands between the two.

Many modern consumers don’t realize the major disparities when they look at the stone at first glance. Far too many assume that the weight of the stone works the same as gold does, where it’s a set price for everything.

That’s not true.

Carats measure the mass of something, but doesn’t tell us about how pretty the stone is, how rare, or if it comes from a prestigious mine. Carat weight tells us just the mass of the stone, but will not give us any info on the color or saturation, how balanced it looks under certain light, or even the grade of the cuts r treatments that are done on such a stone.

Pricing stones come with a variety of factors that you need to be mindful of when getting into the gemstone trade.

Compare sapphires beyond carat weight

Browse rough and loose sapphires with color, dimensions, cut and treatment disclosure in mind.

Browse sapphire gemstones

1. The Carat Weight Fallacy: Weight Is Mass, Not Face-Up Size

Carat comes from the carob seed used by middle Eastern and Mediterranean cultures as a means to balance out the scales and determine the weight of items. As a measurement, it’s about a fifth of a gram. It will never measure anything more than just how much mass Astone has.

Specific Gravity and Visual Presence

There are a varieties of different minerals out there with different specific gravity due to the chemical makeup of the stone itself. How this is determined is through specific gravity, which determines the density of minerals in comparison to water. To explore another species mentioned below, visit the natural spinel gemstone collection.

Here’s a few examples: 

• Emerald (Beryl): SG of 2.67 to 2.78
• Diamond: SG of 3.51 to 3.53
• Spinel: SG of 3.58 to 3.61
• Ruby & Sapphire (Corundum): SG of 3.98 to 4.05
• Zircon: SG of 4.60 to 4.70
• What this means is, the higher the specific gravity, the smaller the stone will be. 

A sapphire and emerald, both cut the same way, will differ in weights even fi they are the same size, because corundum weighs a lot more than emeralds. 

You need to factor in the stone’s surface area when buying gemstones, because you may be paying for a lot more than you realize.

Study a cushion-cut aquamarine

Review this 4.95-carat loose aquamarine as a practical example when comparing shape, face-up appearance and stated weight.

Shop this aquamarine

The "Belly Cut" and Optical Windowing

Most lapidary cutters will remove the rough material in order to keep the most weight possible instead of focusing on beauty. This differs from diamonds, which are given specific cuts that will determine the best reflection and light possible. A colored stone will have much larger depth, or a heavy belly to keep the weight, making the pavilions of these stones a lot smaller. 

Stones that have too large of a pavilion end up carrying a lot of dead weight, especially when put into jewelry pieces. 

There are some stones that have the opposite problem though, where a window is cut, making the stone look a lot more washed out when light hit it, making it look dull when set. 

A gem that’s 1.5 carats that’s precision cut will have the geometry faceted as best as they can, no windowing, and scintillation that shows off brilliance. This will cost a lot more than a gem that’s double in size, but carries so much excessive weight and looks bland under light.

2. Color Science: The True Arbiter of Colored Gemstone Value

Color is responsible for almost three-quarters of the market value of a stone according to findings by the GIA Colored Stone Grading System, . color isn’t’ just whether a stone looks blue or green. It discusses how saturated the stone looks, any notable hues, and the tone under certain lighting.

Hue: Primary and Modifying Hues

Hue is how the color of a stone looks when light hits it. Most natural stones won’t have a pure color, it will have a variety of colors added to it. 

Emeralds will look green in most cases, but may have a bluish hue to it, making it a very expensive stone compared to one that’s yellow.

Sapphires that are a velvety blue or royal blue under light always price higher than those that look gray or green.

Tourmalines that have various different hues, sometimes pinks and sometimes chrome colored. Many buyers want the chrome ones sourced from Pakistan because of the vanadium and chromium in it. For a species-specific discussion, read the tourmaline value and price-per-carat guide.

Tone: The Perils of Extinction and Washout

Tone determines the relativity of darkness and light. 

This ranges from 0, which is colorless, to 10 which is black.

Most gemstones are anywhere between 4-7, so about medium dark. 

Many buyers shy away from high-tone stones because it causes the stone to look kind of black, hiding the color of the crystals and only looking vibrant under certain lighting.

One example of such tone-rich stones is the Basalt-hosted sapphires from Thailand and Australia. These look very iron-rich because they are very high on the scale.

The opposite is also a problem. If it’s a 3 for instance, it tends to have a more watered-down color. 

This can still look nice, but it does markedly affect pricing.

Saturation: The Primary Price Multiplier

Saturation is the strength of a color’s hue, and is the most important factor when determining a stone’s price.

If the saturation is low, it can look almost brown or gray, sometimes rust-colored if the stone is red. 

High saturation tends to look very pure and rich under lighting. You’ve probably heard a stone be called vivid or intense. That’s high saturation at work. 

This can affect two stones of the same weight and species. If an emerald has a gray-green color versus the other which has an almost vivid green-blue going on, the one with the vivid colors can be five, sometimes ten times the price.

Look at color variation in spinel

This 200-carat Mogok spinel parcel offers multiple faceted stones for comparing hue, tone and shape rather than weight alone.

Shop the Mogok spinel parcel

3. Clarity Demystified: Why Diamond Standards Ruin Colored Gem Appraisals

Diamonds are beautiful specimens, but so many buyers will determine their piece based off the diamond criteria. Problem with that, is that diamonds are homogenous in formation, while a colored gemstone has many more factors that play a part in the vibrancy of the stones. Sno two colored stones are made the same way.

The GIA uses this clarity scale for gemstones that have colors: 

• Type I (Aquamarine, Morganite, Tanzanite, Blue Zircon): Crystals these grow without inclusions and is eye-clean. If there are inclusions, it drastically affects price. 
• Type II (Ruby, Sapphire, Spinel, Garnet, Tourmaline): has visible inclusions. While eye-clean does offer a more premium price, you’re allowed to have inclusions so long as it doesn’t ruin the brilliance. 
• Type III (Emerald, Red Beryl, Sphene): these guys benefit from having inclusions, and are judged based on the stability of the structure rather than the presence of occlusions alone.

The Emerald Jardin

Emeralds are special, because they’re made through the commingling of beryllium and chromium, with trace amounts of vanadium in metamorphic veins. Most emeralds have some form of inclusions, whether it’s a crystal, a gas bubble, or a fracture that’s healed, called a Jardin.

Emeralds aren’t judged by having inclusions, but instead on the transparency. If a Jardin looks neat and is glowing under light, it’s super valuable. If there are inclusions that affect the structure, it can completely tank the price. For a real listing to examine alongside these factors, review the 3.20-carat emerald-cut green emerald.

4. The Geographic Origin Premium: Provenance as an Economic Multiplier

The origin of the stone is also a part of the pricing. Two stones could have their prices differ by the thousands based on where it comes from. It isn’t just how it looks either. Sometimes, the reputation of the mine affects the price. Explore the Kashmir sapphire rarity, history and value guide for an origin-focused example.

Emeralds: Colombia and Swat Valley vs. Commercial Deposits

• Muzo and Chivor, Colombia: most Colombian emeralds don’t’ have much iron because they’re made through sedimentary rocks. The chromium is much more vivid compared to others, and tends to not be low in saturation. Columbian emeralds do make the premium almost double, especially compared to Zambian or Brazilian of the same size. 
• Swat Valley, Pakistan: Swat valley is another notable stone because of the vanadium and chromium in these stones, making them look even greener than Colombian specimens. Most Swat emeralds are very small, only a couple carats, but can be much more expensive compared to others. 
• Panjshir, Afghanistan: Panjshir emeralds are very transparent and have the most even crystal structures. The hues are unlike any other, and will command a high price. 
• Zambia & Brazil: Zambian emeralds are much more bluish-green compared to the others on the list due to the iron amounts in each stone. Brazilian emeralds are commercial grade, and tend to be much cheaper when priced against a Colombian or a swat valley emerald.

Sapphires: Kashmir and Ceylon vs. Basaltic Fields

• Kashmir: the Kashmir mine was initially found in the Himalayas after a landslide, and is one of the most famous mines of all time. The mine sources cornflower sapphires of a rich royal blue that look almost silklike, and have been a favorite for over a hundred years. However, due to the mine being exhausted back in the 1920s, these emeralds also fetch a large sum because they are rare and not mined anymore. 
• Ceylon (Sri Lanka): another notable mine, these sapphires are also blue and cornflower, and look beautiful. Most Ceylon sapphires are priced as luxury goods. 
• Basaltic Sapphires (Australia, Thailand, Nigeria): these sapphires contain a ton of iron and look almost inky and dense. Most Austrian sapphires tend to be much lower in price compared to a Kashmir or Ceylon stone of the same weight.

Tourmalines: Paraíba and Himalayan Mint vs. Standard Greens

Tourmalines are much more straightforward compared to the others on the list. Most standard ones go for up to a few hundred dollars, but if the stone is copper-looking or has a neon Paraiba to it, the price then goes up by a hundred times, so you’re looking at over fifty grand a carat. 

A radian tourmaline that looks almost mind-colored that comes from the Pakistani and afghani pegmatite veins are incredibly valuable as well, especially when pitted against green albite from Africa. This stone in particular is increasing markedly in value. For an example of rough material, examine the 100-carat Afghan rough tourmaline parcel.

5. The Treatment Multiplier: The Natural, Unheated Reality

Treatment is another major factor in pricing.

• Untreated stones are those that look how they were sourced, and usually only get the lapidary cut. This accounts for less than 2% of most stones, especially sapphires and rubies. 
• Heat treatment is when the stone is treated using very high temperatures, usually to get rid of inclusions and really highlight the saturation and hue. This type of treatment is praised in the business, but it does lower the price slightly when compared to a gem that isn’t heated.
• Oil and a resin treatment is used for stones with lots of inclusions in order to make the fissures less visible. Most use cedarwood oil to treat the stones, but some will use epoxy reins. However, it does significantly lower the value. 
• Lattice and diffusion treatment is used to help fill in and remove any fractures. While it looks nice, it will completely tank the resale value of the stone, and is not used as often. 

So what this means, is a two-carat Ceylon sapphire that isn’t heated and has the right documentation will carry a price increase of up to 300% compared to the same stone same size that has gotten heat treatment.

6. Real-World Case Studies: Same Carat, Radically Different Invoices

Understand what cutting removes

Follow the rough-to-ring yield guide to see how crystal shape, fractures and cutting decisions affect finished gemstone weight.

Read the gemstone cutting yield guide

7. How Savvy Buyers, Cutters, and Jewelers Value Stones

Here is what most buyers are using to determine stone value. 

1. The stone is viewed in natural light as the standard, along with indoor light. A stone with high value will remain saturated in different environments, without looking black or gray. 
2. Check dimensions along with the carat weight, and then check to ensure you’re paying for the surface area facing up rather than hidden weight underneath or a pavilion that’s too thick. 
3. Don’t ignore type II rubies or Type III emeralds if you see inclusions. Focus on whether those inclusions will effect transparency or durability 
4. Get an appropriate certification from a notable lab 
5. Choose a mine-to-market supplier that’s reputable, such as Folkmarketgems to get rid of any markups and ensure you’re getting a stone with the right disclosed treatments and authentic that is legitimate.

Frequently Asked Questions (FAQ) 

1. Why does a 1-carat sapphire look smaller than a 1-carat emerald?

The specific gravity is different, which affects the size of the stone. 

2. Does an eye-clean emerald always cost more than an included one?

If there’s a lot of saturation, yes. Pale emeralds without inclusions actually are less valuable than those with brilliant colors and a present Jardin.

3. How much does geographic origin really impact gemstone price?

Depending on the location, such as Kashmir or Swat Valley, it can make the stone up to 10 times more valuable.

4. What is windowing and does it reduce value?

Windowing is when light spills out due to the facets being pavilion, making it look more dull and lifeless. 

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