A Closer Look at Gemstones
Being familiar with the characteristics of a gemstone can go a long way towards helping make good designing decisions. Not all gemstones are appropriate for all applications, so having a working understanding of certain terms can aid in unlocking a gemstone's potential.
Hardness can be described as a gemstone's resistance to being scratched, or conversely, its ability to scratch other things. The scale we use to measure a stone's hardness is called the Mohs Hardness Scale, and it runs from 1 to 10. Your fingernail is about a 2-1/2, a dime is 3-1/2 and glass is a 6. We have probably all seen a movie or TV show where a person scratches glass with a diamond. Diamond, at 10 on the Mohs scale, is the gold standard of hardness. It is extremely resistant to scratching, and can scratch most other things. It is for this reason diamonds are used so often in industrial applications, such as sanding, drilling and cutting. Because of its hardness, diamonds are the ideal stone to use in designs that might have to stand up to a lot of wear and tear, such as in a wedding ring.
On the other end of the scale is talc. Talc is so soft that it won't scratch anything. Because of its low Mohs score, talc probably wouldn't be used in any jewelry application. It is much more common to see talc in its powdered form, which is used in wood-working.
Fluorite, Mohs hardness 4
Turquoise, Mohs hardness 5 to 6
Smoky quartz, Mohs hardness 7
Being aware of a gemstone's hardness can help determine what sort of jewelry it is appropriate for. You might be less inclined to use fluorite, with a Mohs hardness of 4, in an everyday bracelet or ring that gets banged around a lot because it is much more prone to scratches. Stick to earrings and necklaces or special occasion rings and bracelets when designing with this particular stone. Garnet has a Mohs rating of 7 to 7-1/2, so it's a great choice for rings and bracelets.
Cleavage and Fracturing
Gemstones break in two ways; they can cleave or they can fracture, and in some cases, both can occur. Gems that cleave tend to break along planes of weak atomic bonding. Atomic bonding refers to the attractive force that exists between atoms. They will typically break along lines that are parallel, perpendicular or diagonal to the crystal faces. Fracturing stones break along planes that have nothing to do with atomic bonds. Fractures are typically uneven, and each kind of fracture has its own descriptive name. Conchoidal (shell-like and scalloped in appearance) is the most common kind of fracturing found in gemstones.
Just like with hardness, cleavage and fracturing can influence what gemstones you would want to use in jewelry. Emerald is a terrific example of the way cleavage affects gemstones. Have you ever noticed emeralds are cut in an emerald cut more often than any other shape? Even though emerald is a beryl, which is a 7-1/2 to 8 on the Mohs scale, it is prone to cleavage, so it is cut this way to help prevent chips. It is important to remember that hardness is different than a stone's tendency to cleave or fracture. For instance, a diamond has the highest level of hardness, but it can still be damaged by a strong strike because it can be cleaved along its weak atomic bonds.
Cleavage Fracture in Labradorite
When thinking about what stone to use in a design, optical properties carry a lot of weight. Color plays an important role in design, but luster is also important. Luster is determined by the way light reflects off the surface of the gemstone. The categories of luster are: adamantine (diamond), vitreous (garnet), metallic (pyrite), resinous (amber), dull (coral), greasy (jadeite), waxy (turquoise), pearly (pearls) and silky (malachite). Luster can affect how a piece looks, so it is an important factor for designers to consider. If you are looking for a very shiny gemstone, vitreous gemstones such as garnet or amethyst would be a good choice. If instead you would like a raw organic look, possibly resinous amber or dull coral would be the most appropriate choice.
Gemstones are complex things, each having its own "personality." Understanding a particular gemstone's characteristics can help you design a beautiful and long-lasting piece of jewelry.
For more information about individual gemstones, visit the Gem Notes info section in our EncycloBEADia®.
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"Love the article about gemstone characteristics and what to consider when using them."
||We would like to share some of the customer comments we received in response to the article "A Closer Look at Gemstones," 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.
"I learned a lot from the article. Thanks!"
"This article on gemstones was new to me. Mind you I can't afford to use gem stones, but now I can look and understand them with a more knowledgeable eye. I do enjoy all the articles you put out, thank you,"
"Love this type of info"
"I liked the article very much--helpful and instructive, as are all of your resources. I just wish that you would make them easier to find. I seem to find them almost by accident. Would it be possible to have an index showing where information can be found? Or perhaps this already exists--but if so, it's hard to find! Thank you!"
"This is the second article on gem stones that has been so informative. I like to know the 'personalities' of a gem, and having studied geology I find these articles most helpful and educating. I like to learn, and these articles do a great job of teaching. Keep those gem stone "gems' coming."
"Make this into a table I can print to have it, great information."
"This article is very helpful. Thank you."
"I really enjoyed reading this article. It will help me immensely with my jewelry design as I am just staring this endeavor. Thanks"
"Loved the article. Anything I can learn about gemstones is great. Years ago you sent me a catalog and when I opened it I fell in love with gemstones. I especially love the jaspers and agates with their beautiful glossy strength and stunning visual patterns. Like any lover I can never know too much about my beloveds. Thanks FMG!!"
"The article on the gemstones was very good. I liked the mohs identification on the gems. That will help alot when you are making jewelry. It was also interesting to know about the fractures that these stones can go through. I liked the article very much."
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