So you want to begin gem collecting…What are the most important factors to consider? Since it’s October, we will begin to assess the answer using its two birthstones: opal and tourmaline. 

First and foremost, at Omi we believe the gemstone must evoke your own sense of awe and curiosity. We hope it sparks passion, because that is what drives us too! No two gemstones are alike, and this is especially true when it comes to opals and tourmalines. 

What value factors do collectors consider? Understanding the range of available types and colors of particular stones, will help you understand why one is more valuable than another. Value of colored gemstones considers several attributes, which are similar to the 4C’s used to grade diamonds: cut, color, clarity and carat weight. 

Set with a 2.85ct Paraíba-Type Tourmaline, displaying exceptional clarity and fine greenish-blue color

Without question, Paraíba tourmaline is considered the most expensive and valuable type of tourmaline. But within that distinction, there is a range of hues and saturation levels across Paraíbas that increase and decrease value. Typically the more pure “Windex” or “neon” blue the stone, with little to no green modifiers, the more valuable the stone. There is also clarity to carefully consider when purchasing a Paraiba tourmaline. This variety is often included because of where and how it grows, so understanding the degree and range of acceptable inclusions is important. 

Set with 6.42ct. Indicolite Tourmaline

Indicolite, is the non copper-bearing blue variety of tourmaline. Rubellite and chrome tourmalines are examples of reddish-pink and green varieties respectively, and fine examples of all three can command high prices. This is also true for parti-colored tourmalines; the most common being combinations of pink and green. However, single tourmalines can display multiple colors, and typically the more distinct colors present, the more valuable the stone.  

Two examples of Rubellite Tourmalines

Judging and collecting opals values color slightly differently than in a faceted stone, like tourmaline. In opals it’s important to consider the number of colors present in its play-of-color pattern. Similarly important, a collector must consider the saturation of color and the pattern it appears in. Larger patches of color in a pattern, will typically be considered more valuable. While red is the rarest and most valuable single hue within an opal. 

Both opal designs above display a pinfire pattern, but the second ring displays a greater variety of colors within its pattern.

Further, opals have what gemologists refer to as “bodycolor.” Black opals, which are often the most valuable, will have a dark base or “body” color. This typically allows the color to appear much more saturated, versus white opals or crystal opals.

This 9.54ct opal ring displays a classic black body-color.

And even still, all these factors only apply to phenomenal opals. There are still other varieties such as fire opal, Peruvian blue opals and pink opals. All are made of crystallized silica, but these opals will never command the same prices as their phenomenal counterparts. 

At Omi, our goal is to ensure our customers and clients can discover new and rare gemstones to add to their collection, support them to buy with confidence and develop the tools to become discerning gemstone connoisseurs. If you have any questions about value factors for a particular gemstone – please reach out to us at – we would love to hear from you and answer your questions!