Tuesday, May 5, 2020

ROCK'N RESOURCES FOR TODAY

While many of our favorite rock shows, stores, and club meetings are shut down to prevent the spread of COVID -19, it's a good time to dig through our personal stockpiles and work on them at home.

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
Fred
While it may be fun to just hold it up and say, "This is Fred!" that's not exactly a scientific name and doesn't do anything to help you know how to work on it. Here are some tips and resources to identify your mineral.

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.
If you get a chance to visit the Lyman Museum in The Lyman Museum in Hilo, HI, do it just for the crystals.  It is one of the few museums in the world that displays its mineral collection by the Crystal System rather than by the mineral type.

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
Luster: Vitreous-Silky
Mohs Hardness: About 6
Streak: Colorless
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.

That linked to a page with a rock that looked just like mine! BINGO! It also gave me tons of information about my rock. The most important was that it contains asbestos. So if I decide I want to work on it, I'd better be sure to wear a good mask!

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).

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BOOKS

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,

Donna


     
     
     







Sunday, April 5, 2020

The Uncommon Beauty of Common Opal

Pendant of Precious Opal






Before I became a rockhound, I thought that opal was the flashy stone often found in rings and earrings.That type is called precious opal.  I love it, but as a lapidary I find it terribly expensive and that makes me nervous to work on it.










For lapidary purposes, I personally prefer common opal. It comes in an amazing range of colors (Colorless, white, yellow, red, orange, green, brown, black,  and blue) and patterns, making it a great material for my lapidary fun. I've even used it in two of my lapidary meal displays!

The Opal Fish slab shown with veggies



The first part was a hunk of white, banded common opal that looked for all the world to me like a slab of cooked halibut. That led me to create my first meal case I show at lapidary club shows and a county fair. Notice how the natural lines in the opal help give it that "fishy" look!






Green Opal Pickle Relish

The second was a chunk of green opal that made me think of hamburger pickle slices. I'd just started working on a hamburger meal at the time and I blythely put it into a saw to slice without examining it closely. This was the moment I learned about how easily common opal
can fall apart. The sound it made when it exploded in the closed saw was amazing.  Stopping the saw and opening the top, I was treated to a view of thousands of small bits of green opal everywhere in the saw, including the oil. Once it was cleaned up, I decided the bits looked a little like pickle relish. So I added a few small shards of red glass, and my repurposed opal was ready.

OTHER THAN AS A FOOD SUBSTITUTE

Australian Dendritic Opal



The range of common opal that is suitable for cabochons is almost limitless. The solid colors are beautiful, but since opal tends to take more of a lustre than a shine, opal with dendrites and other inclusions makes a cab with a story to tell.

In my shop, I like to work with this material. At between 5.5 and 6.5 on the Mohs Scale, it works fairly quickly, but is hard enough to hold up a bit and not disappear under the wheel.  Like I said above, the finishes aren't shiny, more of a luster. The dendritic  "kite" shows a shine at the center because the light was right over it there.

Here's a lovely piece of Blue Opal I'm looking forward to working on. It has a few gold-colored imperfections, but to me,they help tell the story.


SHOP TALK

Because common opal is amorphous (lacking a natural shape, not crystalline: perhaps a geletain
mineral), it is classed as a mineraloid. It also contains water that can range from 3 to 21 percent of its weight. It occurs in fissures of other rocks, giving it its shapes. That moisture level is why some dry out and crack. If you've purchased some opal at a show and it is in a container with water, it's probably best to keep it that way or it may craze, fracture, or lose its color.

Boulder Opal from Australia








I chose this boulder opal, not because of the precious flashes--it doesn't have any--but because the clarity of the opal shows how the bits of debris settled at the bottom when the opal was still a gelatin. If you can enlarge this image on your screen, you'll see what I mean.






 SOMETIMES - JUST LOOK AT IT




Especially when I'm at shows, I tend to find opal specimens that are just incredible to look at, and I'd never want to cab.  This limb-cast is from the Blue Forest in Eden Valley, WY--which was a forest once, eons ago, but is desolate now.


Blue Forest Opal

Please send your comments about common opal to Donna@LapidaryWhisperer.com

Be sure to visit my next blog post on May 5.  It's all about ROCK'N RESOURCES FOR TODAY! You'll love it!

Donna
Your Lapidary Whisperer