A gemstone (also called a gem, fine gem, jewel, precious stone or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli) or organic materials that are not minerals (such as amber or jet) are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemsA gemstone (also called a gem, fine gem, jewel, precious stone or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli) or organic materials that are not minerals (such as amber or jet) are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone. Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a lapidary or gemcutter; a diamond worker is a diamantaire.
The traditional classification in the West, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious; similar distinctions are made in other cultures. In modern usage the precious stones are diamond, ruby, sapphire, and emerald, with all other gemstones being semi-precious. This distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent with fine color in their purest forms, except for the colorless diamond, and very hard, with hardnesses of 8 to 10 on the Mohs scale. Other stones are classified by their color, translucency and hardness. The traditional distinction does not necessarily reflect modern values, for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald. Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone. Use of the terms 'precious' and 'semi-precious' in a commercial context is, arguably, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, which is not necessarily the case.
In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al2O3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the Emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow), and morganite (pink), which are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum. Material or flaws within a stone may be present as inclusions.
Gemstones may also be classified in terms of their "water". This is a recognized grading of the gem's luster, transparency, or "brilliance". Very transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency....more
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There were only the great diamonds and sapphires and emerald mists and velvet inks of space, with God's voice mingling among the crystal fires.There were only the great diamonds and sapphires and emerald mists and velvet inks of space, with God's voice mingling among the crystal fires....more
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―
Ray Bradbury,
The Illustrated Man
There's a world full of wonder and magic. This place is known as Trollzopolis. Five girls--The B…more
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There's a world full of wonder and magic. This place is known as Trollzopolis. Five girls--The Best Friends For Life-- are responsible for keeping it safe. Originally there were Amethyst, Sapphire, Topaz, Onyx and Ruby, but now that those five have become elders, its up to five new teens to protect the world that they dearly love, mentored by the Obsidian and the Originals. The new generation consists of Opal Trollangel,
Do you love rocks, minerals & crystals?!
Let's read books w/gemstones featured in the title or …more
[close]
Do you love rocks, minerals & crystals?!
Let's read books w/gemstones featured in the title or plot.
There are so many ways to organize this & so many possible books! So, how about we give each letter of the alphabet a go, then we can start over. I'll post a 'new' gemstone each ?month?, but you can read at your own pace. No pressure, no strict 'follow the leader,' you jump in where you want!
I'm not including author names, because it would be nice to have an actual stone show up in our reading...but this is your challenge, too, so modify it however works for you.
Nonfiction that focuses on a particular stone is fine, too.
Steven universe, you know the show but there were also the other gems. The runaway gems. The gem…more
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Steven universe, you know the show but there were also the other gems. The runaway gems. The gems ran away from home, escaping from the wars hundreds of years ago.
There's a world full of wonder and magic. This place is known as Trollzopolis. Five girls--The B…more
Do you love rocks, minerals & crystals?!
Let's read books w/gemstones featured in the title or …more
Steven universe, you know the show but there were also the other gems. The runaway gems. The gem…more