Monday, August 5, 2019


 The first time I saw this incredibly blue chunk of what looks like part of a limb, I had to have it. I'd never seen anything like it before. Petrified wood with blue bark! It looks to me as if the blue chalcedony formula changed a bit over time as the material directly in contact with the wood is darker than the material on the top. It appears that it once was botryoidal but the cool bumps were worn down.

It turns out there is only one area known to have this particular material; the Blue Forest at the west end of Eden Valley, Wyoming.  Don't let the the name of the place fool you, it may have been a forest in the Eocene Era, but now it's pretty desolate now.



This image of Blue Forest petrified wood where the chalcedony filled the center, shows both gradation of color due to minute changes in the mineral content of the water when it was formed as well as a botryoidal lining in the center.

Side comment, I love to say the word botryoidal. It's somewhat lyrical. Don't know how to pronounce it, check out Daniel's example at Here


In the Blue Forest of Wyoming, about fifty million years ago, it is believed that a volcano erupted in the region, knocking the trees over. The area where they fell is swampy and algae quickly enveloped the wood, preserving the shape. Over countless years, the wood cells themselves decayed and the space was taken by agate, quartz and silica primarily, along with a variety of minerals. There can be a range of blue colors created by the inclusion of tiny amounts of manganese, iron, copper and titanium.

Credit: Jim Snowden

This cool image of botryoidal blue is courtesy of Jim Snowden at Blue Forest Petrified Wood Their site is one of the places I visited when I researched this blog post. I encourage you to visit them for information or to purchase amazing specimens.


Some of my Arizona wood showing blue.

While this area is unique in its presentation of petrified wood with blue chalcedony bark and inclusions, blue chalcedony is not, itself, rare.  Blue can also be found in other petrified woods, especially from Arizona, where the wood is often multi-colored. 

In the image at the top, the wood did not shrink as it was being petrified and you can see that the wood grain was very well preserved. In some cases, the wood has shrunk creating voids that are filled with the blue chalcedony, which leads to . . .

Blue Forest with gold chalcedony 
At the San Francisco Mineral & Gem Society show this weekend, I saw (okay, I bought) this chunk of rock from the Blue Forest. I took the picture dry, but wet, even the wood has a blue hue. In this case, the bark is rough golden chalcedony. In this situation, when the wood petrified, it shrank, allowing flows of blue and gold chalcedony and a bit of white quartz. It reminds me of some boulder opal I got some time ago, except that while the blue is lovely, it's no opal!


I've made a number of cabochons from petrified wood. They chatted with me and helped me create some amazing cabs.  If you're hoping to see an image of a Blue Forest cab here, it may be a while. So far I can't bring myself to slab my new acquisition even though it is thick enough, and I'm afraid if I try to slab the quarter-round specimen at the top, the blue will detach.  Darn.

Have you ever worked with this material? I'd love to see your photos!

Until next time,
Your Lapidary Whisperer,

Friday, July 5, 2019


My Mariposite yard rock.

The green and white that make up Mariposite make it an attractive yard rock. But as they say in the television commercials, there's MORE!


When miners during the California Gold Rush discovered they could find gold and placer gold in the green and white rocks around them instead of standing in a cold creek with a pan, they named the rocks Mariposite for the town they were standing in. (Not a huge imagination happening here, but a great way to tell others where to find it).

It can be found in many areas around the world, where it is mostly called Mariposite, except for Canada where they call it Virginite for some reason. Now, if you want to check my research, please check for Virginite on Google. When I checked on Bing, their articles under "virginite" were not about rocks. Nuf said.


It's actually not a mineral. Depending on how you want to think about it, it's either a metamorphic rock or a conglomerate. Chromium-rich Mica give the rock its green color and its flash. Dolomite Marble or Quartz provide the matrix. 

Mariposite slab


 That depends on your willingness to handle disappointment. First, let's examine the hardness on the Mohs scale of the mineral which compromise the rock

Mica       2.5-3 
Dolomitic Marble  3.5-4
Quartz  7

As you can see, the Mica and Marble are similar in hardness, but soft as heck. If you want to cab it, plan on making it into a pendant where the edges are encased or it won't last long.  When the Mica is next to Quartz, undercutting is a real problem. 

I decided to create some Mariposite flowers for this blog post. Not my best idea ever. You can see that  I got one (of several tried) flowers. The plan was to make three and make a divot in the center that would hold a crushed yellow rock/epoxy mix to make it look like a flower. 

Flower start in Mariposite 

The first one came out fine. A bit rustic, but that was what I was looking for.  The others, even though I was using 220 grit and higher, shattered. Apparently, this rock is known for, basically, falling apart. I plan to try to get some more done so I can make a flower arrangement, but I think I'll need to drop them on the floor first to see where the slab breaks naturally.


Aside from gold mining and cabs, Mariposite has traditionally been used for other practical purposes including being a facing stone for buildings or fireplaces and even markers in cemeteries (although I suspect they weathered so quickly that their messages were soon lost).

Have you worked with Mariposite?  What was your reaction?

Until next time, your Lapidary Whisperer,