The 4Cs stand for cut, color, clarity and carat weight and are used for grading gemstones. These factors have an effect on the value and price of the stone. It’s important to have a good understanding of these four factors when buying any type of gem, to know exactly what you’re buying. It will also give you the tools you need to play around with the combination of the 4Cs to find stones that are give you a great balance between value and appearance. Here’s how to evaluate a gemstone, using the 4Cs.

Cut

The ‘cut’ of a gemstone refers to its shape, proportions, and its final touches like the faceting and the polish. When it comes to evaluating some gemstones, such as diamonds, the cut is the most important of the 4Cs. The cut determines how much light can pass through the stone, impacting its brilliance and sparkle.

For diamonds, cut is the most important of the 4Cs. A diamond may have excellent color, carat and clarity, but if it doesn’t reflect light effectively, it can appear dull. Instead of reflecting light back up, it will allow it to leak out from the bottom, thereby reducing its sparkle. Proper proportion and cut will result in optimum brilliance.

For colored gemstones, cut isn’t the most important factor. This is because light performance isn’t the main consideration with most gemstones. There can be other variables that can affect the cut of a colored stone. If a gem is too dark, for instance, the stone can be cut shallow which would improve its color, but reduce the brilliance. On the other hand, a very light colored stone can be cut deeply to make it look darker.

The shape of a raw gemstone (also called the ‘rough’) often determines the cut of the stone. Jewelers typically cut gemstones in a way that will allow them to retain as much as possible of the rough. They cut the stones into various shapes including ovals, hexagons, triangles, rounds, cushions, emerald, pears and hearts, to name a few. There are numerous types of gemstone cuts and some are better suited for certain types of stones than others. Some gemstones (like opals) are too soft for certain cuts, whereas others may be too brittle.

Color

Color is another important factor that affects the value of any gemstone. It is divided into three main components: saturation, tone and hue.

• The saturation is the intensity of the gemstone’s color, ranging from light to vivid. Usually, gemstones with high color saturation are the rarest and most highly valued. As the color saturation of the gemstone decreases, so does the stone’s price.
• Hue is what we call the actual color of the gem. Nearly all colored gemstones have primary and secondary colors (or hues) and some even have a third. However, the stones free of secondary or tertiary colors are considered the most valuable.
• The tone of a gemstone is the lightness or darkness of its color and gemstone variety has an ideal tone. Typically, stones that are either too light or too dark cost less since their tone differs from the ‘optimum’ tone.

In general, gemstones with pure colors, high saturation, and medium tone are far more valuable than others. For example, the most valuable variety of emerald is intense green without any yellow blue tones.

Clarity

The clarity of a gemstone refers to either the presence or lack of inclusions in the stone. This can affect its appearance, durability, and value.

All gemstones have various types of inclusions such as fractures, hollow areas, minerals, or gas bubbles within them, which can reduce the overall value of the stone while also affecting its appearance. Inclusions act as obstacles which don’t allow for free passage of light through the stone. They can also be unsightly, especially if located in a highly visible area. This is why highly included stones are less expensive than stones with fewer to no inclusions at all.

When grading gemstones, gemologists note the presence of inclusions that can be seen by the naked eye. If the stone doesn’t have any impurities, the gem is considered ‘eye-clean’ and more valuable. If the inclusions are visible without magnification, it can impact its value and desirability.

However, not all gems are graded the same way. In fact, there are three types of clarity categories that all gemstones fall into.

• Type I – Stones in this category are usually eye-clean. These include aquamarine, morganite, smoky quartz, tanzanite, tourmaline, zircon, and heliodor.
  • Type 2 – Usually included. Some examples are iolite, peridot, quartz, spinel, alexandrite and andalusite.
  • Type 3 – Almost always included. Examples include emerald and red tourmaline.

Some gemstones have inclusions deep inside them which can weaken the gem, making it prone to breaking. This is why these stones aren’t ideal for jewelry that receive a lot of abuse. If there are fractures deep inside the gem, they can burst and cause the stone to crack.

Carat Weight

A carat is a unit of weight used to measure gemstones and is equal to 200 milligrams or 1/5 of a gram. The carat weight of a gemstone is important for its price and value.

For most gemstones, larger gemstones are usually less common than smaller stones, which is why they cost more per carat.

Here’s an example:

A quarter-carat citrine may cost about $15 and a half-carat citrine which has the same clarity, cut and color grades as the quarter-carat stone may cost about $50 in total. A larger, one-carat citrine with the same grades can cost up to $100. A .25 carat diamond may cost $500, but a 1 carat diamond can cost $10,000. As you can see, the increase in price is not linear, but exponential.

When calculating carat weight, the size of the gemstone isn’t taken into consideration. Carat weight is all about the ‘weight’ of the stone. Since the density of every gemstone is different, two different gemstones of the same size will likely have different carat weights.

In Brief

Knowing the 4Cs can be useful when shopping for a gemstone to avoid being scammed and buying a lower quality stone for a higher price. It’s important to remember that higher grades aren’t a guarantee that the stone looks great. You might be able to find stones at lower prices which look excellent to the naked eye.