UV Fluorescence in the High Desert

The other day while out attending to chores about a mile and a half from the main buildings on the estate I came across an interesting piece of chalcedony out in the desert.  Tucked up next to a mesquite bush this unusually shaped piece of chalcedony looked more like a cartoon mouth or a rock shaped box that formed when the the quartz was liquid and flowing creating a shape I'd never seen before.  Finishing my chores, I shoved it in my pocket and continued walking back out of the desert.  Back at the estate one of the first things I checked after cleaning the stone was it fluorescence.  Using a short wave UV light, which I use to check bedding at the Painted Pony Resort, the specimen fluoresced green. A previous post about fluorescence shows both yellow and green fluorescent chalcedony found around the estate and this specimen gets added to the pile of big and little specimens that when illuminated with short wave UV light re-emit light at a visible wavelength. 

I use a 395-410 nm UV light to illuminate the desert and look for a variety of fluorescent plants such as lichens, animals, and rocks at night.

Chalcedony specimen under normal lighting.

Chalcedony specimen with short wave UV light fluorescing green.

Chalcedony found around the Painted Pony Resort.

More Gifts From the Ants.

While testing the idea of harvester ants as a rangeland health monitor species, small crystals from the ant colony mounds were collected and sorted.  Below are small (~3 mm) specimens of chalcedony found outside colony entrances.  The image was taken using a digital dissecting microscope.  While the second image is the same grouping but photographed under UV light with a camera.  Note several of the chalcedony pieces fluoresce with a greenish light.  This behavior was also noticed in larger chalcedony specimens collected from the high New Mexican desert around the Painted Pony Resort.

Chalcedony specimens collected from the mounds surrounding harvester ant colonies.

The same grouping of chalcedony but under UV light.

Fluorescent Desert II

Some more camera work with the black light and rocks from the desert.  Some specimens of Chalcedony fluoresce under long wave UV light appearing both green and less commonly yellow.  While the majority of chalcedony specimens collected do not fluoresce those that do, stand out on the desert landscape at night under UV light and are easy to find.  The short video below shows fluorescence from mineral and biological sources.  The orange appears to be from some species of lichen which is brown under visible light but bright orange under UV while the remainder of the fluorescing specimens are chalcedony. 

Chalcedony, Cyrptocrystalline Quartz

Chalcedony, a cryptocrystalline form of quartz, is a frequent find while out on the landscape around the Painted Pony Resort.  Pieces of various sizes are often found in association with archeological sites or found siting isolated on the surface.  Chalcedony forms from low temperature silica rich solutions and exhibits a pleasing convoluted form which is easy to spot while walking.  Generally smooth in appearance with a waxy luster, in some cases the specimen will be covered in a layer of small quartz crystals which sparkle in the sunlight further highlighting the specimen on the ground.  Unlike large single or multiple crystals commonly associated with quartz the crystalline formation of Chalcedony results in smaller crystals and the overall appearance is a translucent light colored rock with convolutions.  Formed in veins, chalcedony is found in a variety of host rock (including basalts) filling cracks and crevices.  Although no veins of chalcedony have been located in either mountain range the presence of specimens in the valley suggest veins of chalcedony exist somewhere locally. 

Evidence of the use of chalcedony by prehistoric peoples in the area is shown in the second image below.  The base of a translucent chalcedony lanceolet projectile point found about 1 mile west of PPR in the Amigos del Cielo air park suggests that not only did earlier residents find chalcedony pleasing in shape and appearance but also a useful source material for tools.

a 2" x 4" Chalcedony specimen

Chalcedony arrowhead base