info@1800loosediamonds.com
You've probably heard of the 4Cs of diamond quality, but the process for grading colored stones isn't as clear cut. There aren't such clearly defined standards for grading a colored gemstone, so while the 4Cs of diamond quality are still used to put them into a category, color is going to be the primary consideration when determining the quality of the stone.
Stones are found in a huge variety of colors and each color has its own set of criteria that plays a role in its grade. Use this guide to help you understand the grading scale so that you know what to look for when you purchase a piece of jewelry.
Before we talk about how gems are graded, let's look at the types of gemstones that exist, both precious and semiprecious. There are many to choose from and each is graded in a variety of ways. There are two types. Read more about them below.
Gemstones are beautiful on their own, but to create a piece of jewelry that you are able to wear, they must be set in some type of metal. While the metal can affect the value of the piece, it isn't taken into account when grading the stones. There are some common precious metals that appear often in jewelry, but others aren't used as predominately. Choosing which one is best is largely based on personal preference, so choose the one that you think looks best with your gemstone. Choices include:
Types of Gemstones
Before we talk about how gems are graded, let's look at the types of gemstones that exist, both precious and semiprecious. There are many to choose from and each is graded in a variety of ways. There are two types. Read more about them below.
Diamonds and Colored Stones
All stones that aren't diamonds fall into the colored stones category. The main four precious stones are as follows:- Diamond
- Emerald
- Amethyst
- Ruby
- Sapphire
- Garnet
- Aquamarine
- Onyx
- Pearl
- Opal
- Turquoise
- Jade
- Lapis lazuli
- Topaz
Color
In some sense, color is a subjective method of classifying a colored gemstone. After all, the way you see a royal blue stone may differ from the way someone else sees it. While colors like this used to be used to describe colored gemstones, the jewelry industry has worked to create descriptions for colored stones, which include hue, tone and saturation. Let's look at each a bit more closely.Hue
The hue of the stone refers to its place on the color wheel. Because some stones are a combination of colors, they are also included in the hue choices. These hues are loosely based on the Munsell color system but are modified to fit the colors that tend to appear in various stones. While there tends to be a list of hues that jewelry graders gravitate towards, some that are rarer may not appear on the color grading scale. Examples of the most often-used hues include those listed below. Dominant colors are capitalized, while secondary colors are not. In hues that have two dominant colors, they are also separated by a hyphen.- Colorless
- Black
- Gray
- Brown
- yellowish Brown
- orangey Brown
- greenish Brown
- pinkish Orange
- Orange-Pink
- orangey Pink
- slightly orangey Pink
- Pink
- purplish Pink
- Pink-Purple
- pinkish Purple
- Purple
- reddish Purple
- Purple-Red
- strongly purplish Red
- slightly purplish Red
- Red
- orangey Red
- Red-Orange
- reddish Orange
- Orange
- yellowish Orange
- Orange-Yellow
- orangey Yellow
- Yellow
- greenish Yellow
- Yellow-Green
- strongly yellowish Green
- yellowish Green
- slightly yellowish green
- Green
- very slightly bluish-green
- bluish Green
- very strongly bluish-green
- Blue-Green
- very strongly greenish Blue
- greenish Blue
- very slightly greenish Blue
- Blue
- violetish Blue
- bluish Violet
- Violet
- violetish Purple
Tone
When it comes to the color grades for tone, you will see numbers from 2 to 8. This describes how light or dark a stone is. The preferred tone is different for different stones (sapphire versus emerald), for example, but medium to medium-dark is usually what people are looking for. A stone that is too light will appear pale, while a stone that is too dark may make it difficult to detect its hue. The color grading scale for tone is as follows:- 0 - colorless / white
- 2 - very light
- 3 - light
- 4 - medium light
- 5 - medium
- 6 - medium dark
- 7 - dark
- 8 - very dark
- 9-10 - black
Saturation
The saturation of a colored stone refers to how intense its color is. It's one of the key factors when considering the value of a stone. The colors have saturation modifiers, which can change its pure color one way or the other. For blue, green and violet stones, the modifier is gray. For stones that are red, yellow or orange, the modifier is brown. Therefore, a stone with poor saturation, would have gray or brown listed as part of its hue grade. Grayish-violet, for example. Higher saturation levels are more desirable and increase the value of a stone. Colorless diamonds are classified as being colorless on one end of the spectrum, all the way to light yellow or brown on the other end. Diamonds that fall outside the normal colors associated with the stone are called fancy color diamonds and come in hues like pink, red, yellow, orange, green, blue, and purple. The are called "fancy" followed by the color hue they feature. That includes many colored diamonds, among them black diamonds and those with a brown color.Clarity
The perfect diamond is expected to be free of inclusions, or blemishes that can be seen under 10x magnification. Unlike diamonds, colored stones may be synthetic stones if they appear to be free of inclusions. While a diamond's value increases when there are fewer to no inclusions, a colored gemstone is considered to have high clarity grades if it's eye-clean, which means there no obviously visible inclusions. When a jeweler assesses the clarity of a colored gem, they take into account a couple of factors. That includes the size, location and number of inclusions, as well as how visible they are when looking at the stone. Natural inclusions, including both visible and internal inclusions, occur often and can affect the durability of a jewel. There are several common types of visible inclusions, which you can read more about below.- Cavities - holes that appear on the surface of the stone and move inward.
- Color zoning - bands or areas of alternating colors on the stone.
- Fingerprint inclusions - liquid filled tubes inside the stone that look like fingerprints.
- Halo fractures - also called discord fractures, these circular or oval-shaped blemishes resemble fried eggs.
- Included crystals - minerals inside the gemstone that can appear transparent, light, dark or opaque.
- Liquid inclusions - spaces inside the gem that are filled with liquid.
- Silk - often seen in rubies and sapphires, this refers to fine needle-like structures that may actually add value to the stone because it adds to the brilliance.
- Eye Clean = ~ equivalent to Flawless grades for diamond
- Slightly Included = ~ equivalent to VVS/VS
- Moderately Included = ~ equivalent to SI
- Heavily Included = ~ equivalent to Imperfect, level 1
- Severely Included = ~ equivalent to Imperfect, level 2 & 3
Cut
The term "cut" refers to the facet, shape or style of a stone. This occurs as part of the process of turning it into a piece of jewelry, such as diamond engagement rings, items with colored accent stones or anything that is turned into a sparkling piece. It also refers to the symmetry, proportion or finish of the gem. Lighting environments contribute to the way cut appears so you may have to give up other aspects of the stone to get a premier cut. Diamonds tend to have highly visible properties that contribute to its brilliance and dispersion, which enhances its appearance, and therefore its value. When it comes to colored jewels, the goal is use cut to showcase the best color and don't adhere to the same strict standards as brilliant diamonds. In fact, so-called color rough stones can be more valuable, colored stones are often cut non-precisely. Gem cutters use the following guidelines when cutting colored stones.- Colored gemstones are typically cut to enhance the most attractive color. Because they often change color depending on the angle at which you look at them, the most desirable color is usually cut to appear on the top of the stone.
- The goal is usually to maximize the final weight of the gem. This is influenced by the shape and form of growth of the stone.
- A gem cutter will also work to hide undesirable inclusions.
- Colored stones are often cut to align with fashion trends and styles.
Cut Grade
This grading combines proportion, brilliance and finish, which a grade between 1 and 10. In some cases, there may be overlap.- 8-10: Excellent
- 6-8: Very Good
- 4-6: Good
- 2-4: Fair
- 1-2: Poor
Brilliance Grade
Brilliance can also be thought of as the light return. Keep in mind that, unlike the diamond grading scale, colored stones are rarely classified as being excellent. Here is the scale that is usually used:- Excellent = 75% +
- Very Good = 60 - 75%
- Good = 40 - 60 %
- Fair = 25 - 40%
- Poor = = 25%
Proportion Grade
There are two sub-grades in this category. They are called face-up proportions and profile proportions. Face-up proportions include symmetry flaws and face-up appeal flaws. It also evaluates proportion, using the following scale:- Excellent -- minute variations from ideal
- Very Good - minor
- Good - noticeable
- Fair - obvious
- Poor - prominent
- Symmetry
- Bulge
- Table size
- Girdle thickness
Finish Grade
The finish grade is applied based on facet of the stone. Polish blemishes might be scratches, nicks, lines, or abrasions. Symmetry flaws might be irregular, poorly aligned, or misshapen. Facet symmetry grades come as too few, acceptable, or too many, as related to the size and design of the stone.Carat Weight
The last of the 4Cs of diamond quality is carat weight, which isn't exclusive to the diamond grading scale, as colored stones are also evaluated on their carat size. One carat is equivalent to 1/5 of a gram. Jewelry may be given a carat weight for a single stone, or collectively for a group of smaller stones. Some colored stones are easier to find in large carat weights, while others, such as a ruby or blue stone sapphire are harder to come by in larger sizes. This affects the value of the stones. Often a stone isn't cut to a pre-determined carat weight as this can affect the total weight of the piece. Commercial quality stones are more likely to be pre-calibrated, so you may find that certain kinds of stones are easier to come by in pre-set sizes.Precious Metals That Stones Can Be Set In
Gemstones are beautiful on their own, but to create a piece of jewelry that you are able to wear, they must be set in some type of metal. While the metal can affect the value of the piece, it isn't taken into account when grading the stones. There are some common precious metals that appear often in jewelry, but others aren't used as predominately. Choosing which one is best is largely based on personal preference, so choose the one that you think looks best with your gemstone. Choices include:
- Gold (including gold alloys)
- Colored gold (white, rose, etc.)
- Silver (including silver alloys)
- Sterling silver
- Platinum (including platinum alloys)
Types of Settings
There are also a variety of settings that can be used to create jewelry. They may vary from piece to piece, but in general, you'll see these settings for necklaces, rings, earrings and bracelets. Check them out below:- Solitaire - also called a prong setting, this is the most common and with a basic band and one large gemstone.
- Bezel - a durable choice, this setting is characterized by a thin metal band that goes around the gem and holds it in place.
- Tension - this setting wraps around the gemstone so that it looks suspended from either end.
- Channel - characterized with ridges along the band, the gemstones are held in the resulting channel and is used for sparkle.
- Pave - stones are mounted with small prongs along the band.
- Halo - the center gem is surrounded by smaller gems.
- Cathedral - arches are used to lift the stone setting higher than the traditional solitaire setting.
- Bar - much like the channel setting, but the gems are enclosed by metal bars on all sides.
- Flush - also referred to as the gypsy setting, this one is recognizable by the fact that the stone is inside a hole drilled into the band so it's flush with the band.
- Three-stone - as the name implies, this setting features one center stone, with two others flanking it, often in different colors.
- Antique/Vintage - often featuring fancy or old-world style embellishments, this setting is often found in vintage pieces.
- Cluster - like the halo setting, but instead of one large center stone, there is a collection of smaller stones that resemble a single gemstone.