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Buyer’s Intro to Rubies

What are Rubies?

R11954 | right | medium | play | “Stone ID : R11954 – Weight : 2.13ct – Origin : Myanmar”Rubies are variety of corundum . Pure corundum has no coloration; with the vivid red ruby color comes from trace amounts of the element chromium (Cr). Like other precious stones, finding facet-quality , ruby material usually requires miners to go through tons of rock material before finding any rough, uncut crystals that qualify. Most rubies come from two sources: Myanmar, better known as Burma, and Mozambique. Burmese rubies are considered the standard for rubies since Myanmar is the historical producer of the gem. Other sources can produce material of overlapping color and quality, since ruby material produced from each location is a range of colors and inclusions, though some have region-specific characteristics.

Stone durability is ranked in three parts. First of these is hardness. Ruby is a difficult stone to scratch, sitting at a 9 on the Mohs scale (a hardness ranking that goes from 1 to 10) as a species of Corundum. Diamonds are the only natural stone harder than Corundum.

Toughness, another part of stone durability, is separate from hardness and refers to a stone’s tendency to chip and break. Ruby lacks cleavage planes (places where the stone likes to crack), though does have a tendency to part. Parting is similar to cleavage, but is usually less severe and less consistent in how it is oriented, located, etc. This means rubies are very tough, and very resistant to breaking and chipping.

Mohs Scale
Stone Hardness
Diamond 10
Corundum 9
Topaz 8
Quartz 7
Orthoclase 6
Apatite 5
Fluorite 4
Calcite 3
Gypsum 2
Talc 1

The last part of durability is about the stability of the stone, meaning how much things like light, temperatures changes, and chemicals affect it. Rubies do not react much to light, changes in temperature, and various chemicals. This makes ruby jewelry ideal for frequent use and for pieces that are more susceptible to damage, like ruby rings and bracelets.

Like diamonds; rubies follow the four Cs of color, carat, clarity, and cut, but have different standards. For example: diamond clarity gets ranked at the microscopic level, while rubies are only ranked at what is eye-visible. 

The most important factor in rubies is the color. That famous “ruby red” is the entire factor that separates rubies from pink sapphires, followed closely by carat weight and clarity. Given the fact these stones are priced per-carat, the cut is very often adjusted to maximize the weight. Few colored stones in general are perfectly cut aside from lower-quality, commercially sized ones.

Pricing due to clarity can fluctuate wildly between rubies due to the types of inclusions, their location, size, and number. Sometimes there are inclusions that make the stones valuable like certain amounts of silk (rutile needles). With the right amount and proper orientation, you get a star ruby.

The rarity of a ruby depends on the quality of the ruby crystals. Highly included, opaque rubies are nowhere near as rare as clear, transparent rubies or even clear, blue sapphires. There is also a distinction in how the material is used, with opaque ruby crystals used for carving and transparent ruby crystals used for faceting (this goes for other gemstones too).

Beautiful, facet-grade rubies are a bit rarer than blue sapphires. Larger, facet-grade rubies are significantly rarer blue sapphires. Spectacular specimens like the Sunrise Ruby (weighing 25 carats and selling for 30 million US dollars) have even exceeded $1,000,000 dollars a carat USD.

When choosing a ruby, note that finding one with perfect color, clarity, and cut in anything above a carat will be difficult since they are incredibly rare, especially an untreated stone (over 97% of mined rubies are treated). As such, the Natural Ruby Company is equipped to help find a ruby that suits your tastes based on the 4Cs of gemstone buying:

  • Color
  • Cut
  • Clarity
  • Carat Weight

Ruby Color

When discussing ruby color, it is also necessary to mention that the point between the “pink sapphire” and “ruby” is a heavily contested topic in the gem industry. Every stone is a unique combination of colors, and what is considered a pink sapphire in America might qualify as a ruby elsewhere in the world.

Ruby color is not a single color, but a range. It goes from pinkish red, to purplish red, to orangish red, and an unmodified ruby red as well. There are even star rubies, which we have available at the Natural Ruby Company.

R7699 | “R7699”R4704 | “R4704”R12010 | “R12010”U12034 | “U12034”R2178 | “R2178”

There are three main components to any color; hue, tone, and saturation.

Hue – The actual color, as in red, blue, yellow, etc. The stones above are an example of this. Very often there are modifying colors like purplish red, orangish red, etc.

Different Basic Hues

Purplish Red

R12057 | “R12057 ”

Red

U12034 | “U12034”

Orangish Red

R12010 | “R12010”

Tone – How light or dark the stone is. Note that rubies (aside from star rubies) do not have light tones. These are pink sapphires by definition. Their tones only go from medium like U12034 to dark like R7697.

Different Tones

Dark

R7697 | “R7697”

Medium

U12034 | “U12034”

Light

P3996 | “P3996”

Saturation – How pure the color is. This is the difference between having ruby red and a reddish brown. It can also be the difference between a ruby and a pink sapphire, or brown corundum.

Different Saturations

Brown

CR2353 | “CR2353”

Brownish Red

R2005 | “R2005”

Red

U12034 | “U12034”

Ruby Cuts

R9046 | right| play | “Stone ID : R9046”If choosing a specific ruby red proves difficult, there are other options to help narrow the search. There are a variety of cuts that gemstones come in, including one-of-a-kind cuts  like the ruby to the right.

Some common cuts are:

R11955 | “R11955 Round”

R12009 | “R12009 Heart”

R12538 | “R12538 Marquise”

R11954 | “R11954 Cushion”

R12012 | “R12010 Oval”

R11757 | “R11757 Trillion”

R12008 | “R12008 Pear”

R11951 | “R12951 Emerald”

The cut of any gemstone is unique based on potential inclusions, pleochroic color, quality of the crystal rough, and ultimately how the cutter adapts to all these factors. No two gems will be exactly the same unless cut exclusively for that purpose, especially in larger carat sizes.

Most colored gemstones have a modified step cut on the bottom, like the round, cushion, oval, pear, marquise, trillion, and heart shapes listed above. The only exception to this is the emerald, which has a completely different cut. Other cuts like radiant and princess are more uniquely cut too, but much less common since they are not as adaptable as the modified step cut.

About Ruby Clarity

R10825 | right | “Stone ID : R10825”Rubies can be transparent and clean looking (with inclusions difficult to find even with magnification), but these are few and far between. Clarity affects the price of rubies based on the type, location, number, and size of the many possible inclusions. These factors can dictate a large part of the price.

R11277 | left | “Stone ID : R11277”Having inclusions in the center of the stone with R10825 one the right is less attractive than having those same inclusions towards the edge at the girdle in R11277 on the left. Inclusions around the edge can be hidden in a setting too, depending on the location and desired setting. Once the stone is set as a ruby ring, ruby necklace, or whatever piece of ruby jewelry is preferred, inclusions often become much less visible. Note these are magnified images of the actual rubies, meaning these inclusions are much less visible in person.

Common inclusions in rubies :


Silk in a Mozambique Ruby
(Rutile Needles)

Crystal Inclusions
(Rutile Crystals)

Discoid Fractures
(Tension Halos)

Fingerprint Photo by Ted Themelis

Pinpoints, Clouds (groups of pinpoints), and Rutile Needles

Color Zoning Photo by Ted Themelis

The status of inclusions can reveal whether or not a stone has been heat-treated. Most rubies (and sapphires) have been heat-treated to improve clarity and color of the stone, and their price reflects this as demonstrated below. These effects are stable and widely accepted in the gemstone trade with disclosure.

R11949 | medium | “R11949 – 1.11ct – Heat Treated $3,885 Per carat”R11756 | medium | “R11756 – 1.32ct – Untreated $9,775 Per carat”


Characteristic silk in a Burmese ruby
from the famous Mogok mines.

There are other natural factors associated with clarity, including the host material for rubies. There are two main types, one marble hosted and the other basalt hosted . Marble hosted rubies often have a brighter, softer red partially due to having a certain amount and types of inclusions (like rutile needles, aka silk). Basalt hosted stones are often darker and clearer looking, often lacking any silk.

U11962 | medium | “U11962 Marble- hosted Myanmar Ruby”

R7052 | medium | “R7052 Basalt-hosted Mozambique Ruby”

Note that the keyword above is often and not always, as nature is rarely consistent and full of special exceptions. It is very possible for an untreated Mogok ruby to not have any silk, and a Mozambique ruby to be full of silk.

About Carat Weight

Carat weight is another factor that determines not just price per carat, but also what type of jewelry stone gets made into. Particularly large, and subsequently heavier stones usually are not chosen to make something like ruby earrings and might be worn more comfortably as a ruby pendant.

It is worth mentioning that rubies do not typically grow over a carat. This is because the element that causes the red color, chromium, is relatively rare. Rubies also form shallow, tabular rough, restricting cutters from faceting large rubies. This makes anything over a carat exceptionally rare.

Rarity and Price

The price-per- carat of rubies, like any gemstone, increases exponentially with the carat weight. For example; two 1 carat rubies will be worth less than a single 2 carat ruby of comparable quality. Why a difference in price even though the carat weight is the same? Because a 2 carat ruby is that much rarer than two 1 carat rubies. Unlike color or even cut, carat weight cannot be gained, though it can be lost with re-cutting and re-polishing of the stone.

R6660 | “R6660 1.25ct $4,187.50”R11666 | “R11666 1.07ct $4,750.80”R5346 | “R5346 2.16ct $16,329.60”

In this instance; the two-carat ruby is worth more than double the two 1 carat rubies combined.

Final Choice of Rubies

While there are a number of factors that determine market value for rubies, the most important factor here is whether or not you are satisfied with the stone. Everyone has different preferences, and not every preference will lead to the industry defined “ideal ruby”.

Each stone is a unique profile of clarity characteristics, coloration, cut, and weight. Even if every stone were cut to the same calibrated specifications, the type and arrangement of clarity characteristics all tell different stories. Some labs try to document these details in order to identify gemstones after being recut, much in the same way as people identify themselves with fingerprints.

Ruby Heat Treatment

U5546 | medium

U5546 Untreated 1.07ct from Mozambique Price : $6,000 Per Carat

R11835 | medium

R11835 Treated 1.02ct from Mozambique Price : $3000 Per Carat

These two stones are very similar down to color, cut, carat weight, clarity, and even source, but the untreated ruby is double the price of the treated one because of how rare it is to find a stone with the same properties straight out of the ground. While the exact percentage will fluctuate, over 95% or even 97% of all mined material gets treated (most common one being heat-treatment).

Heat-treating rubies is widely accepted in the industry with disclosure due to the improvement in color, clarity, and the fact that it is a permanent, stable treatment.