Rocks & Mineral Identification-A Rockhounder's Guide : eBay Guides

This is not for the serious collector who spends big bucks on specimens, nor someone who wants an appraisal on their collection.  This is for the person who loves rocks, buys them because they look pretty, or goes out in the hills to treasure hunt.  Most of us remember collecting rocks as kids.  We didn't care if they were valuable.  We just cared that they were pretty and we enjoyed them.  Mine I kept in a flowerpot in my window, and then later in a garden in my front yard.

I'm writing this guide to help you understand a little better what some of these minerals may be or how to find more of them.

First off, what is a mineral?   Or a rock?  Wikipedia states "A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.  A rock, by comparison, is an aggregate of minerals and need not have a specific chemical composition.  Minerals range in composition from pure elements and simple salts to a very complex silicates with thousands of known forms.  To be classified as a "true" mineral, a substance must be a solid and have a crystalline structure.  It must also be a naturally occuring, homogeneous substance with a defined chemical composition."

Rocks can be one mineral if they are massive, but are more commonly several minerals cemented together.  They can also be organic (amber, fossils...), or like obsidian; a natural glass that varies in chemical composition.  Or even a meteorite!

Currently there are more than 4000 known minerals, according to the International Mineralogical Association, who approves and names any new minerals found.  Of these, about 150 are considered common, 50 are found occassionally, and the rest are rare to extremely rare.

Whether buying on ebay or searching outdoors, it really doesn't matter what you collect, as long as it is a "gem".  Gem or Gemstone are not scientific words.  Both rocks and minerals can be gems.  Gems are chosen by their beauty, their wearability, and their rarity.  But beauty is in the eye of the beholder!   So if it looks good to you, it's worth collecting!  The old way of classifying rocks as precious or semi-precious is really not accurate, because some rocks are far more rare and valuable then the precious stones the general public knows!

So without an expert in your pocket, or some very expensive equipment-how do we know what we are buying or collecting?  Here are some suggestions of what to look for:

Appearance-  a magnifying glass can help and natural sunlight is best.  Many minerals are well known and easily identifiable by their color.  Malachite is a banded green.  Turquoise a sky blue, and Pyrite is called "Fool's Gold" for a reason!  Of course other rocks and minerals can be these colors too.  And some minerals can actually vary in color.  Turquoise can be green.  Other things we can look for are transparency-can you see light through the rock?  Translucent means you can see light, transparent means you can see through the stone.  Generally the clearer the stone is the more valuable it is.  Agates tend to be translucent, whereas Jaspers usually aren't.  We can check out the luster.  The luster of a stone can be metallic (hematite), adamantine (sparkly), vitreous (shiny like glass), resinous (semi-glossy), pearly (has an iridescence), chatoyant (has a glowing effect), or silky (fibrous).  Tiger eye is known for its chatoyant gold color.  The firey glow of opal or fire agate is easily spotted.

Hardness-Everyone has heard of the Mohs Scale, invented in 1822 by a German mineralogist named Friedrich Mohs.  He determined that diamond is the hardest mineral known to man (10), and that talc is the softest (1).  Then he designed a scale from 1-10 so that each mineral on the list can be scratched by any of the minerals below it, and in turn it can scratch any of the minerals above it.  The difference in the hardnesses is not necessarily equal (say from 10 to 9 is not the same difference as from 5 to 4).

The scale is:

1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Feldspar
7. Quartz  (the most common rock found and generally considered to be the first of the "hard" rocks)
8. Topaz
9. Corundum
10. Diamond

You can buy inexpensive kits with items to test hardness, or you can use household items.  A good steel knife blade is a 6, glass is a 5.5, a copper penny is a 3, and a fingernail is a 2.5.  And by the way, hardness has nothing to do with breakablity!  Diamonds can be broken.  When rockhounding, some rocks can easily be broken up with a hammer, others you'll really have to work at.  Jade is the toughest rock there is.

Weight-  Minerals have different densities.  Some are very light, like amber.  Some are much heavier, like meteorites.  To officially identify a mineral there is equipment to identify its "specific gravity".

Magnetism-  Meteorites generally contain nickel iron and are magnetic.  In fact, besides a metal detector, the best way to find them is with a large magnet.  Magnetite is also able to be picked up by a magnet (hence its name).  Rocks that have iron, cobalt, or nickel will feel slightly magnetic.

Habit-  The "habit" is the tendency of a mineral to grow a certain way.  There is lots of scientific information available in books or on the web, as to geometric shapes and crystal formations, so I won't even try to cover it here.   There are stalactites, stalagmites, botryoidal (bumpy), drusy (covered in small crystals), etc. 

So where does one look for rocks to collect?  Well the easiest way is to visit a rock shop, a gem and mineral show, or shop right here on ebay.  Ask lots of questions.  Like in any field, it is buyer beware.  Look for a reputable dealer who has been around for awhile and has a good reputation or feedback.

If you want to try your hand at rockhounding on your own, be sure to stay safe.  There are lots of good books to get you started on where to look.  Including a great series of Gem Trails of (insert your state here) books.  Make sure you are allowed to be where you are, and that you bring safety supplies-water, gloves, first aid kit, etc.  Bring some hand tools-rock hammers, chisels, etc.  And something to collect in-a bag, or buckets work great.  But most important!  FOLLOW GOOD MANNERS.  Close gates, pick up your trash, avoid driving off the road, and fill in any holes you dig.  Take someone with you and tell someone where you are going. 

Check with your local rock club for field trips or locations.  Another good place to get information is at your local rock museum.

Above all-  HAVE FUN!!   Good luck!

Please be sure to visit my store to see some great rocks and minerals!