Mineral Mondays #35 - Silver Lace Onyx

Silver Lace Onyx is a unique & rare stone. It is only found in the Calico Mountains outside of Yermo, California. Needing to get away from Crypto and Twitter yesterday I took a day trip out to go collect some.

The Gemstone

Silver Lace Onyx is a type of onyx (chalcedony) that can contain minute amounts of silver. Usually white and/or gray in color, it also comes with honey-colored inclusions known as honey onyx. It is considered a semi-precious gemstone and is popular amongst rockhounds and jewelers because of it's lace patterns containing manganese dendrites which when cut and polished make beautiful cabochons.

The material was deposited at its location about 10 million years ago during a volcanic period. The volcanism pushed up hot fluids containing various minerals including silver & gold. The Calico Mountain range was famous in California for being one of the largest silver producers in the 1880's. The mountains​s also contain fantastic agates, jaspers, calcite ​and ulexite, TV rock.

History

Silver Lace Onyx was first discovered in the early 1900's when prospectors were looking for silver and gold in the Calico Mountains. Some of the unique material was found and assayed. While there were minute amounts of silver in the onyx, it wasn't profitable to extract. The mine that produced the material left a large tailings pile in its wake full of material for future rockhounds to collect!

It was named by Lucille Burns McShan Coke who lived in the valley below and used to collect the rock as a little girl because it was white. She helped introduce this beautiful stone to the lapidary community around the 1950's.   

Localities

As mentioned above, this type of onyx is only found in the Calico Mountains, specifically just off of Mule Canyon road at the entrance to the canyon.

Some Silver Lace Onyx Facts

• Shape - nodules, veins 
• Composition  - Silicon Dioxide (SiO2)
• Hardness - 6.5 - 7
• Refractive Index - NA
• Color  - White, gray, honey, with black & silver maganese veining.
• Localities - Calico Mountains, Yermo, California 

Conclusion

One of the better pieces I was able to find. This is a fine specimen with all of the qualities a lapidary would want to work with.

Thanks for reading!

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