Color variations are caused by impurities within the stone, typically other minerals alone or in combination.
There are different categories of colored stones.
|Idiochromatic: Some gemstones are called idiochromatic, or self-colored. These stones are colored by an essential part of their chemical composition. For instance, you cannot have peridot without iron--it is an essential part of the gemstone. Iron is also what makes peridot green. Therefore, all peridot is green. An idiochromatic stone will ALWAYS be a particular color since there is no way to remove the impurity that lends the stone its color without changing the nature of the stone.|
|Multicolored: Tourmaline is a fine example of a multicolored stone. Within one crystal, different levels of impurities will produce a wide variety of shades and colors.
Color is one of the most appealing aspects of gemstones, and an important factor to consider when designing jewelry.
|Interference happens when light reflects off of structures within a gemstone. Iridescence, such as seen in opal and labradorite, is an example of interference. The play of color seen in moonstone is referred to as adularesence or schiller.|
|Chatoyancy (cat's eye effect) and asterism (star effect) are also caused by the interference of light.|
|Anything can be an inclusion. Think of a dragonfly trapped in amber--that's an inclusion! Rutiles in quartz and prehnite are also inclusions. Some particularly interesting inclusions are actually gemstones within gemstones.
Inclusions can also be invaluable in identifying a gemstone since some kinds of inclusions only occur in certain gemstones and others occur only in stones from a particular location, such as a distinct water-lily like inclusion found in peridot from Arizona. There are even certain inclusions that can help identify whether a stone is natural or synthetic. An example would be veil and feather patterns that occur in flux-melt emeralds.
Inclusions can add interest and depth to a design. Some designers will actually highlight an area with an inclusion in a stone. And if a person had a cabochon with a star, they may not want to put it in a pair of earrings that wouldn't catch the light in the same way as a ring or a pendant.
Being aware of a gemstone's optical properties can take your design to the next level of beauty, and possibly price point!
|We would like to share some of the customer comments we received in response to the article "Gemstone Optical Properties," as featured in an email newsletter. Please keep in mind that the comments expressed below are those of our customers and do not reflect the views of Fire Mountain Gems and Beads.|
"The gemstone information was very informative and interesting. I really enjoyed it. It made me want to know more about gemstones. Thumbs up."
"Hi, me again. Just commenting on the qualities of gemstones article. I felt like I was back in grad school geology--always loved stones, especially gemstones. Thank you for the swift refresher course. I do enjoy the information you send every week. Always learning something new. That is what makes the company more than just a mail-order house. You care to inform and teach. Thank you."
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