Pricey Pebbles


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You’re on a hike in the woods or a walk on the beach and something on the ground catches your eye. Perhaps it’s an unusual shell, a water-polished stone or a shiny, funky-shaped rock. You pick it up and place it in your pocket for later. If you’re like some of us, it ends up in a not-so-small collection of similar items at home. This really isn’t out of the ordinary. People have been fascinated by precious metals, organics and minerals -- such as gold, pearls and diamonds – for thousands of years.

In fact, today many scientists devote their time to studying these natural treasures. Among these scientists are gemologists – people who study gemstones. So what do gemologists study exactly? For one, the origin of gemstones. By origin, we mean how the minerals are formed. For example, some minerals crystallize from molten magma or volcanic lava. Some are formed, or “grow” on or near Earth’s surface. And others are created when minerals that have already formed deep inside Earth are put under extreme heat or pressure. This is how diamonds are formed. Diamonds are the crystallized form of carbon created under extreme heat and pressure. This brings us to the other thing gemologists study – the structure of gemstones.


Almost all minerals are in some type of crystal form – meaning they have a definite internal molecular structure. This molecular structure is what determines the key physical properties like shape, hardness and color. For example, graphite, another form of carbon, is not very strong -- think of how easily the graphite in a pencil breaks. This is because the carbon atoms in graphite link together in rings. In this formation, each atom is linked only to one other atom.

Now, take diamonds. Diamonds are the hardest mineral we know of, ranking a 10 on the Mohs Hardness Scale. It’s the molecular structure of diamonds that makes them so hard. Diamonds are made of carbon atoms linked together in a lattice structure. Think of the lattice top on a fancy apple pie or a lattice-style trellis for plants on the side of a house. Each carbon atom shares electrons with four other carbon atoms, forming what is called a tetrahedral unit. This forms an incredibly strong molecule. This is why diamonds are used for industrial purposes -- as an abrasive, for drill bits or for cutting diamonds and other gems. In fact, the majority of diamonds mined each year end up in some type of industrial tool rather than on the hands of the newly engaged.

While diamonds are strong and popular, there are dozens of other exquisite – and colorful – stones to be appreciated and collected. Let’s look at some of these natural treasures the world has to offer.

Diamonds

  • Colors - clear, blue, red, black, pale green, pink and violet
  • Hardness - 10
  • Birthstone - April
  • Notes - The Cullinan, a 3,106-carat diamond found in 1905 in Transvaal, South Africa, is the largest in the world.

Photo courtesy ©Lawrence Lawry/Getty Images
Ruby and Sapphire

Ruby

  • Colors - ranging anywhere from a light raspberry red to a rich “pigeon’s blood” red to reddish brown
  • Hardness - 9
  • Birthstone - July
  • Notes - Large stones are quite rare and can be considerably more valuable than diamonds of comparable size.

Sapphire
  • Colors - Preferred: "pure, cornflower blue" – also colorless, yellow, orange, green, pink, purple and even black
  • Hardness - 9
  • Birthstone - September
  • Notes - The "Star of India," which is located in the American Museum of Natural History, is a 563.35 carat star sapphire. It is the largest of its kind on record.

Emerald
  • Colors - emerald green, green or even a yellow-green; transparent, clear, opaque
  • Hardness - 7 ½ - 8
  • Birthstone - May
  • Notes - The Carolina Emerald (found in Hiddenite, North Carolina) is owned by Tiffany & Co. of New York. It weighs 13.14 carats.

Photo courtesy ©Lawrence Lawry/Getty Images
Garnet and Peridot

Garnet

  • Colors - golden yellow to orange, red-brown to rose-red to deep violet-red, and lime-green to emerald green
  • Hardness - 6 ½ - 7 ½
  • Birthstone - January
  • Notes - Like diamonds, garnets are also used in industry - as an abrasive. Garnet-coated sandpaper has been in use since 1878. It is widely used in woodworking, as it produces a very smooth finish.

Peridot
  • Colors - yellow-green to olive green
  • Hardness - 6 ½ - 7
  • Birthstone - August
  • Notes - The largest cut peridot is housed at the Smithsonian Institute in Washington, D.C. It is a 310-carat stone.


Photo courtesy ©Lawrence Lawry/Getty Images
Amethyst

Amethyst

  • Colors - pale lilac to deep purple
  • Hardness - 6 ½ - 7
  • Birthstone - February
  • Notes - The largest amethyst ever discovered in North America is two feet long, two feet wide and one foot high and weighs 165 pounds. It was found in North Carolina and is on display in Grandfather Mountain, NC.

Tanzanite
  • Colors - ranges from deep sapphire blue to amethyst and violet
  • Hardness - 6 ½ - 7
  • Birthstone - Tanzanite is not a modern birthstone
  • Notes - Discovered in 1967, it was originally called “blue zoisite” but was renamed tanzanite in honor of the only place it is found -- Tanzania.

Amber
  • Colors - most commonly a golden yellow to a golden orange color, within a broader range of yellow to brown; also green, purple and even black
  • Hardness - 2 – 2 ½
  • Birthstone - Amber is not a modern birthstone
  • Notes - Amber is a non-mineral or organic gemstone. It is the fossilized resin of tres and is millions of years old. Amber often contains visible organic matter like bugs and moss.

The Mohs Scale
The Mohs Scale is used to determine the hardness of solids, especially minerals. It is named after the German mineralogist Friedrich Mohs. The scale reads as follows, from softest to hardest with an example mineral for each level:

  1. Talc - easily scratched by the fingernail
  2. Gypsum - just scratched by the fingernail
  3. Calcite - scratches and is scratched by a copper coin
  4. Fluorite - not scratched by a copper coin and does not scratch glass
  5. Apatite - just scratches glass and is easily scratched by a knife
  6. Orthoclase - easily scratches glass and is just scratched by a file
  7. Quartz - not scratched by a file
  8. Topaz - scratched only by corundum and diamond
  9. Corundum - scratched only by diamond
  10. Diamond - scratched only by another diamond

Try this:
Using this Web site http://www.jewelrymall.com/states/, find out which states produce amethyst, aquamarine, citrine, diamond, emerald, garnet, pearl, peridot, ruby, sapphire and turquoise. Create a graph showing what you’ve found. Next, go to http://express.howstuffworks.com/exp-birthstone.htm, and look up your birthstone. Now, go back to this Web site: http://www.jewelrymall.com/states/. What states produce your birthstone? Now look up the same information for all birthstones. Which modern birthstone is found in the most states?