And, if you're like me, you'll find that you 'rediscover' rocks you'd forgotten about, forgotten what the were, or never really knew in the first place.
So, this month I'm blogging about identifying those mysterious treasures. Here's mine
DO A MOHS TEST ON IT:. Interesting factoid: The earliest known mention of comparing the hardness of one stone vs. another was by Theophrastus in his treatise On Stones c. 300 BC. according to Mindat.org. In 1812, Friedrich Mohs, a German geologist and minerologist developed the scale used by rockhounds and many others today. This is a very helpful diagram from the National Park Service that shows a way to do rough testing by scratching with common objects.
CHECK FOR CRYSTAL SYSTEM
The shape of the crystals helps identify your specimen. As a rockhound, I've found that remembering cubes are isometric and pyrite is gray cubes, makes identifying it by the crystal or the formation of crystals much easier.
There are six crystal systems. All minerals form crystals in one of these six systems. Although you may have seen more than six shapes of crystals, they’re all variations of one of these six habits. Each system is defined by a combination of three factors:
- How many axes it has.
- The lengths of the axes.
- The angles at which the axes meet.
While the crystal system is easily understood, describing all the aspects of it takes a bit of space. If you want to learn about them, I found the explanation at the Gem Society is excellent. Check it out at HERE
ONLINE IDENTIFICATION HELP
If you want to discover what your mineral is on your own, try Identification Process HERE
This is an amazing page designed to help teachers learn the process so they can teach their students. It has excellent, simple instructions and lovely pictures for every step.
HOW I USED IT
Some years ago, I purchase a dark green specimen of undermined origin at an estate sale. It is a dark gray/green color and the crystals look like columns. (See Fred at top of blog) Some of the columns were quite thin, making me think of mica, but they weren't flaky like mica. I decided to use the process I referred to in the paragraph above. Here's what I found:
Color: Dark Green/Gray
Mohs Hardness: About 6
Specific Gravity: I skipped this step and figured I'd go back and do it if the other tests did not get a result.
When I had the information, I clicked through to a page they link to in order to see what I had. They came up with fifteen minerals, and rather than make the mess going back and getting specific gravity, I clicked on the first mineral on the list: Actinolite. This mineral is a combination of basic calcium, magnesium and iron silicate.
If you have access to Facebook, check out Rock Identification You don't have to be a member to see it, but if you want to have your rock identified, you need to join the over 42,000 rockhounds who are already members. This is not a sales board, there are others for that. However, that nifty rock your grandfather gave you when you were a kid may just turn out to be something interesting!
I had one rock that I tried the Identification Process on and couldn't come up with a good answer. I had figured it was about 8 on the Mohs scale, but the drill point I used may not have been what I thought it was. I went to the Facebook group. After some back-and-forth among the group, it was decided that it was Quartzite. (Mohs 7).
There are two books I go to again and again, sometimes to help with identification, and sometimes because they are so darn pretty!
GEMS, CRYSTALS, & MINERALS by Anna S. Sofianides and George E.Harlow (Simon and Schuster) says it is "A comprehensive illustrated guide to the history, lore, and properties of these natural formations." This book is the closest thing to rock porn I can imagine.
GEODES: NATURE'S TREASURES by Brad L. Cross and June Culp Zeitner, (Gem Guides Book Company, Upland, CA) If you're like me, you've picked up geodes from more places than you can remember, and cherished every one. This book has everything you could ever want to know about Geodes and beautiful full-color images. This is where I learned that the inclusion in one of my geodes that I thought was iron, was actually sphalerite.
Now is a great time to check out the mystery minerals in your shop. Work with the resources I've outlined above and let me know how it goes for you!
See you again on June 5!
Your Lapidary Whisperer,