One of the questions I get asked frequently is what distinguishes one gemstone from another. The name of the gemstones we know and love, sapphire, emerald, ruby, etc., are names that were given to them thousands of years ago when gemstones were categorized by their color alone. Science has taught us that gemstones are actually categorized into mineral types, and each mineral type is distinctive from each other because of its chemical composition and its crystal structure. For instance, just because a sapphire and tanzanite are both blue, they are very different minerals. A sapphire is an aluminum oxide and has a hexagonal crystal structure. A tanzanite is a calcium aluminum silicate and has an orthorhombic crystal structure. The differences also give each mineral different optical and durability characteristics.
Interestingly, some gemstones can be part of the same mineral family yet display different colors! For instance, emerald and aquamarine are part of the beryl family but emerald is green and aquamarine is blue-green or blue! In those cases, the crystal structure is not dependent on the color causing element, so it can be replaced in nature by another trace element that changes the color.
Corundum: Sapphire and Ruby. Corundum comes in all colors of the rainbow, including red which we call ruby and blue which we call sapphire! Each color of corundum has a different trace element that causes the various colors. For example, chromium causes corundum to be red (ruby), titanium and iron cause corundum to be blue, and iron alone causes corundum to be a pale yellow!
Beryl: Emerald, aquamarine and green beryl
Zoisite: Tanzanite
Olivine: Peridot
Quartz: Amethyst, citrine, smokey quartz, rose quartz
Garnet: Garnet is not a single mineral, but describes a group of several closely related minerals. We usually think of the brownish red color to describe garnet, but garnet can be other colors too! Green garnets can be either tsavorite (the ‘t’ is silent) or demantoid. Spessartine garnets are golden and rhodolite garnets are purple-red.
Being a Graduate Gemologist is a little like being a detective! Since each gemstone has different optical and visual properties, there are a number of tests with various tools I use to determine what a gemstone is. It is always fascinating!
I would love to help you with your special purchase or custom design! Angela Cisneros Jewelry Concierge brings back the joy and confidence of jewelry shopping, so that you can celebrate with ease! My by-appointment approach means:
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Expert help from a Graduate Gemologist with 23 years of experience (yep, that’s me!)
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*Photo credit of the Sapphire crystals and cut gems by The Gemological Institute of America