Like a lot of things in life, you get what you pay for…..
Precious stones include diamonds, rubies, emeralds & sapphires. That is it. Everything else is considered semi-precious. However, some semi-precious stones can command prices comparable to diamonds & even more (Candy Apple Red Spinel, Mandarin Garnet, Tsavorite garnet, Rubellite & Pariaba tourmaline to name just a few.)When considering a gemstone purchase, it helps to understand that different stones are held to various standards. While the grading criteria for diamonds is well known and encompasses everything from perfect (flawless=$$$$) to highly included (I3=cheap), & a given designation tells you a lot about what that stone looks like, other stones are a bit less regulated.
Semi-precious stones are usually rated as either “facet grade” or not (sometimes called “bead grade” or “rough cut”). This is fairly self-explanatory as stones that are clean enough to be cut into gems and set in metal are “facet grade” & opaque or included stones are generally cut into beads for stringing. Stone varieties are divided into 3 groups. A good quality Type I should be flawless or nearly so. Visible inclusions drastically reduce their value. Type II stones typically have small, inconspicuous inclusions that do not detract from their beauty or compromise their strength or durability. Type II & III stones are often described as “eye clean” (meaning you can’t see any inclusions with your unassisted eye) or “loupe clean” (meaning inclusions require more than a standard 10X jewelers loupe to be seen.) Type III stones almost have some degree of visible inclusions. These may be major or minor and may affect their suitability for jewelry. Below is a list of the most common stones in these categories.
Usually eye clean
Chrysoberyl, yellow and green
Quartz, amethyst, citrine, ametrine
Tourmaline, all but green, red and watermelon
Zircon, all but blue
Almost always included
Emerald, Red Beryl,
Tourmaline: red and watermelon
Sapphires & rubies are corundum (technically, rubies are red sapphires), so inclusions are expected. Some very fine sapphires & rubies are quite clean (though almost never flawless), but very expensive. The amount of inclusions in sapphires can vary with the color family as well. Some blue sapphires & rubies can appear almost translucent, rather than transparent & still be quite valuable. White, yellow and pink sapphires tend to be cleaner. The best rubies come from Burma (Myanmar), but with the long-standing embargo, most Burma material available today is old (i.e. estate pieces). Africa also produces some very nice rubies. Sometimes rubies are “fracture filled” or “glass filled” to improve their appearance by reducing visible cracks & enhancing clarity. These can be excellent values as long as you know that they have been treated & pay accordingly (i.e. they should be relatively inexpensive). Here again, it pays to purchase from a trusted source. Any major purchase should come with a certification from one of the main laboratories, GIA or IGI in the USA or SSEF in Switzerland. These labs will test & certify the country of origin & document any treatments. Certifications generally run several hundreds of dollars or more, but if you are paying big bucks for a natural Burma ruby, but sure that is what you are getting.
Emeralds virtually always have considerable inclusions. They are commonly oiled to improve their appearance & this process is well accepted in the industry, but must be disclosed by US law. Since emeralds (Mohr’s=7–>8) are somewhat softer than diamonds (Mohr’s=10) & sapphires (Mohr’s=9), their flaws make them even more prone to breakage and generally they are not recommended for everyday wear.
In this photo you can see some examples of common inclusions. What are inclusions anyway? They can be a bit of contaminating material, foreign minerals, air bubbles, cracks or debris. They can look like little black or brown spots, fuzzy areas, bubbles of gas, cracks or fissures. The later are functionally important as cracks & fissures can lead to the stone’s breaking either when being set or in wear. Some types of inclusions are actually desirable–we’ll explore that next week.