Gem Type

For an engagement ring, you really want a very hard and durable stone.  Sapphires are an ideal option, ranking high on the Mohs scale, but if you are okay with a stone that might have some wear over time, other options include garnet and spinel.  We do recommend sapphire as the best choice, but regardless of what you choose, it is important to insure your ring against damage!

Color

The first thing on people’s minds when selecting a colored gemstone is obvious: color! It is the most important factor, especially since gems can be found in nearly every color of the rainbow. With thousands of gems to choose from, our search filters make it easy to find one with the perfect hue in our extensive inventory.

Keep in mind, though, that a gemstone’s color can appear slightly different depending on the lighting. Dark and hazy stones can appear even darker in low light conditions, while unheated sapphires can often take on a slight gray tone in incandescent lighting. Most blue-green sapphires will appear slightly bluer outdoors in daylight, and slightly greener under LED light. While our product photos are carefully calibrated to be as accurate as possible for daylight conditions, we have a risk-free review policy to help you see your top choice in person.

Treatment

Many gems are treated to improve their color or clarity. Treatment is not necessarily undesirable- it is just crucial that the treatment be disclosed, something we always do and stand behind with our authenticity guarantee. 

Sapphires are typically heated to improve their clarity and color. The reality is, the best clarity and color are typically the result of heat treatment— which is why globally, around 95% of all sapphires will be heated. In general, if you can find an unheated sapphire with identical size, clarity, and color as a heated one, the unheated stone will be more expensive as it is vastly rarer than its heated counterpart. 

Emeralds are typically treated with fillers like oil or modern resins to improve their clarity. Most aquamarine has been heated at low temperatures to deepen the color and shift it towards blue and away from green. Tanzanite gets its deep blue color from heat treatment. Other gems like spinel, garnet, and tourmaline are almost never treated—because there are few or no treatments that can improve their appearance. 

This is a complex topic which varies for every gem type. Take a deeper dive with our articles on the Heated vs. No Heat Sapphires and on the heat treatment of Tanzanite.

Gem Shape

Different shapes of gems come and go in popularity. While some classic shapes are always in style, like a round cut, hexagon and pear shapes have experienced intermittent bursts of popularity in the past decade. Classic shapes like rounds and ovals also typically have excellent performance in terms of sparkle and brilliance- not every shape will perform as well.  This is a function of the physics of light and the gem in question.  For example, long marquise cuts with their narrow points look great in diamonds, but do not perform well in almost any other type of gemstone.

Some shapes are just extremely rare because the raw gems are rarely suited to be cut into those shapes.  Sapphires in pears and marquise cuts are great examples- it is much more common for a rough sapphire crystal to be best suited to a round, oval, square or rectangle shape, and to cut in a sharp point would be wasting a portion of a perfectly good gem. Given that rough gems are exceedingly rare, extremely expensive, have taken millions of years to form deep underground and then been mined with great effort, we simply cannot justify wasting anything when cutting them! If you can’t find the exact shape you want in the color you want, you will have to decide if shape or color is more important and adjust accordingly.

Gem Size

Gemstones are measured by their weight in carats, but because different gem types have widely different densities, you should make sure to consider their size in millimeters as well.  For example, a round diamond weighing 1.00 carats will typically have a diameter around 6.4 millimeters, but a 1.00-carat round sapphire will only measure about 6.0 millimeters across on average. The length of a gem in millimeters gives a more accurate idea of exactly how big it will appear “face-up”, as when set into a piece of jewelry.

Different shapes will have different face-up sizes for any gem type.  For example, square cushions will usually have the smallest face up size for their weight, while rounds will have the largest face up size at any given weight. The gems in the photo below all weigh the same, but you can see how shape impacts the visual appearance of size.