Gems And Rocks 1

This might be a rather long post so I am going to split it into hopefully only two posts.I am going to talk about  what is a gem and what is just a rock. Don’t get me wrong. A pretty rock is still a pretty rock. However I  buy a lot of beads and I would like to know what I am buying.  I think you might be surprised by some of the information  I am going to give you. Lets start with the most common misconception, thanks to marketers.

Precious and Semi Precious: 

The words precious and semi-precious  have no value. Say What? Those two words have been used to describe gems, but since a diamond, which is considered precious, can sell for as little as $100 a carat ( seen as accents on jewelry) and  garnets, which have been considered to be semi precious can sell for $1000 a carat, there is no value in the description.. Using the  two words is for marketing only as it implies a diamond has more value than other stones.

Diamonds and Colored Stones:gems

Gems have two categories, diamonds and colored stones. Not only are  the two mined different, they are distributed differently. there is a consistent supply of diamonds. Despite what the diamond industry says, there are plenty of diamonds and they are not rare. There are even colored gems that have higher value than diamond. Diamonds, even colored  or colorless diamonds are always considered diamonds.  A colorless sapphire or topaz is still classified as a colored stone. In other words there are Diamonds and then the rest are colored stones.

Synthetic and Homocreate:


Both are man-made but a synthetic gem duplicates their natural counterparts.  synthetic emeralds and  sapphires, look and feel like  the real thing. some are so good that it can be hard to tell  which is the real thing and  which is the synthetic. Homocreate have no real counterparts.  Synthetic garnets like  gadolinium gallium garnet (GGG) and yttrium aluminium garnet (YAG) belong in this category.

Crystalline and Amorphous Materials:

Crystalline minerals are made of a repeating pattern of crystals.  Amorphous means they have no set form or shape.  Not every gem is crystalline.   Amorphous materials can be both organic and inorganic. Examples of organic amorphous materials include amber and ivory. Inorganic amorphous gems include opal, one of my favorite stones.




gemsAggregate means that there are many gems together. Even though an aggregate looks amorphous it is not, it is literally made up of thousands of microscopic crystals.  The most common aggregate minerals is the chalcedony family, which includes agates and jaspers. We find these in our bead stores quite often.  I made a necklace set recently using Picture Jasper. Read about it here:


Ok finally we are to rocks. While crystal and aggregates have a single ingredient , rocks are made up of many different materials. Granite is the most common and well known of the rocks. if you look close at a piece of granite you will find black, gray wand white bits all mixed together. Lapus Lazil is used in gemology but not too many rocks make it into the world of gems.


gemMinerals, Colors and Varieties:

Minerals change the colors or varieties of a gem. Many gems are not pure.  Impurities give them color. Corundum  is colorless when pure.  Add different minerals and you get rubies and sapphires.  The same for emeralds and aquamarines which are minerals added to the colorless beryl .



Garnets are the exception to the rule that pure minerals are colorless.  There are several species and varieties of garnet as well.  Garnets all share the same structure , but they have variations in chemistry. Each of these variations equals a new species of garnet. Common red garnets, most likely the kind you are buying at the gem show, are either almandine or pyrope garnets. These garnets  are deep red. Those pretty purple garnets are  from the  rhodolite species.