Sunday, July 5, 2020

GREEN TREE AGATE: NOT A PLANT


  IMPORTANT NOTICE AT THE BOTTOM 

 

Green Tree cabochon on a shell

 

 

 Green Tree Agate is an absolute delight to work with! With a Mohs hardness of 6.5 to 7, it takes a bright polish, which I always find satisfying.  

 At first glance, it's easy to understand why "agate" isn't the first thing that comes to mind when you see it.  The color is milky white, with no translucence. Also, it's not banded, but it is microcrystalline silicon dioxide, and it is still considered a member of the agate family. 

 

 
Goose in the Garden

 

 

 

This piece of Green Tree was unusually pitted and I was just horsing around with it when a Goose appeared. He's looking left and I don't think he's very happy.

 

 

 

 

 

 

 

DENDRITES OR MOSS?

Then there are the green patterns. Sometimes, they're called "mossy", but in reality, they're dendritic. As far as the color goes, it's not the copper I first thought. It is a combination of manganese and iron oxides. 

 

Those dendrites are what make this stone so much fun to work with. It's almost like watching clouds in the sky, as you look at it, different shapes and stories come alive.  That's the good news. The not-so-good news is that unlike bands in agate, dendrites are in constant motion throughout the rock. The story you see on the slab can easily disappear or become a whole different story as you shape it.

 

Blowing Tree

 

 

When I was making the cabochon at the left, I saw a green sapling in the forest bending over in a storm.

 


 

Frozen Creek

 

 

 

 

 

 

 

I especially love the almost-clear quartz and the darker white material in this cab, to me it looks like a half-frozen stream with evergreen trees along the shore. What do you see? 

 Green Tree agate is most commonly found in Brazil, India, and Uruguay and other colors of dendritic agate can be found in other areas of the world including the U.S.

 

 

IMPORTANT NOTICE

While I love writing the blog, and have since 2016. I find I must take a break from it for a bit. Thanks for your attention and comments. I really appreciate them.  If you have a lapidary topic you'd like me to cover when I restart, please let me know by responding in the Comments section or write me directly at Donna-at-LapidaryWhisperer.com

 

Sincerely,

 

Donna, Your Lapidary Whisperer













Friday, June 5, 2020

CHINESE WRITING ROCK & CHRYSANTHEMUM STONE: Not Where You Think They're From


Since Mariposite is from Mariposa, CA, shouldn't Chinese writing rock come from China?

Nope.

But Chrysanthemum stone does come from China!

Both stones, primarily limestone with with andalusite crystals are rightly called Porphory (igneous rocks that have phenocrysts - large crystals or grains). The limestone is usually dark gray with a slight greenish undertone. The crystals can be close to the color of the limestone. The ones that make for the best contrast for lapidary are white or clear; giving good contrast.

Cab I made with Chinese Writing rock




Chinese writing rocks were first found and described in the 1960's when it was uncovered during road construction in the Sierra Nevada foothills near Auburn, CA. People who saw it thought the random crystal structure imbedded in the base rock resembled characters from Chinese writing, and they really do.

The slab I made this cab from is stained with another mineral. Iron?


Chinese Writing Rock I found in river rocks










This is a Chinese writing rock I found in a bunch of river rock. It has the normal green tones. I keep this one on my desk because I think of it more as a thinking rock, trying to figure out what the shapes might be.







High Quality Chrysanthemum stone Bing Image



Chrysanthemum stone, on the other hand, is found in the Hunan Province's Yangtze River Valley in China. Aside from the geography, the characteristic that divides them is that the dandalusite crystals in the Chinese writing rocks are exceedingly random, the ones in the Chrysanthemum stone are centered with the crystals spraying out in a floral pattern resembling the chrysanthemum flower.





Chrysanthemum stone/yard rock





This, on the other hand, is poor quality Chrysanthemum stone. You can see the flower formations, but they are unclear and unfinished. I got this one at an estate sale for a former rock hound.









IN MY SHOP

My club shop has been closed for a while because of Covid-19, so even if I wanted to harvest a slice off my not-terribly-good-quality Chrysanthemum yard rock, my 10" rock saw couldn't handle it. So my comments will be based on some Chinese writing rock I've managed to acquire.

The Mohs hardness of the stone can range from 5-7, which will have a significant impact on how well it polishes.I've seen other lapidaries do marvelous things with it, but I don't get a lot of satisfaction from the little I've done, like the cab at the top (which I had to use spray sealer to give it a polish--it just looked dead).

So while I love looking at them, neither Chinese writing rock nor Chrysanthemum stone are items I search out.  In fact, if I had a piece like the high quality Chrysanthemum stone above, I'd keep it as a specimen. It's beautiful!

Until next time,

Your Lapidary Whisperer,

Donna