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Next month, we'll be doing some rock hounding in Iron County, Utah. When we were there last year, we spent just a couple hours at some mine dumps west of Cedar City and found some great specimens...several of these turned out to be fluorescent under a standard black light (long wave UV). Since I really want to track down some more of these awesome rocks, I ordered a couple portable UV lamps to bring with us. The first one arrived a few days ago--a 4 watt short wave UV lamp. I hadn't seen any of our collection under short wave UV yet, so I got busy shining it on everything we had. I was excited to see that this lamp nearly doubled the number of fluorescents we have--and some of them are stunning!

A four watt lamp is very low power, but it's enough to examine things (and was all I could afford for the time being). I won't be able to stalk around after dark and shine it on a massive hill of mine tailings and see anything, but it works well enough that I should be able to throw a black tarp over myself and get in close to see if anything lights up.

Here are the photos of our current fluorescent collection. It contains rocks from the Comstock Mine Dump, Iron County, UT; Chalcedony from Brian Head, UT; Rocks from north of La Madera, NM; Petrified Wood from Hurricane Mesa, UT; and some small, bright red specimens from south of Cleator, AZ. Click to view larger versions of the images (the larger ones are better).

Click this link to view large rollover graphic showing all 3 images aligned (550K).

White Light

Long Wave Ultraviolet

Short Wave Ultraviolet

My first attempt at photographing fluorescent minerals was pretty rough. Although the rocks looked great visually, the camera was less than pleased with the situation. I'm currently using a simple black light to do this, and I quickly realized that the huge amount of visible light produced by these lamps tends to swamp the camera's CCD/CMOS. It really overwhelmed the actual fluorescing colors in my first batch, and I had to do a lot of heavy overall correction in Camera RAW and LAB color space.

After doing some more research, I realized that this is just what professional grade UV lights are made to overcome. They are filtered to emit very little visible light, so that everything you do see and photograph is the result of genuine fluorescence. Because I'm not ready to invest in that kind of set up, I decided to piece together a more affordable system and see how I like it. I purchased a Long Wave UV Filter from UV Systems and paired it with a Phillips black light bulb from Home Depot. By positioning the filter above the rock, then resting the black light over the filter, I got an immediate improvement. Visually the difference was apparent, although not really spectacular. However, the photographs benefited immensely. Notice the comparison below.

The first image is from my original set of photographs using a GE black light bulb and no filter. The second image is from my latest set of photos using the Phillips black light bulb and the Long Wave UV Fillter. These are original, unprocessed images, opened using the default Camera RAW settings, with only scaling, cropping and labeling applied.

Original photo using GE UV bulb and no filter
 

Latest photo using Phillips UV bulb and Long Wave UV filter

I've replaced the images in that original post with the new photos, including a new angle of the rock to show a striking sliver of white running across one side.

I had basically given up on a piece of fluorescent chalcedony from that original photo session that glowed with a soft orange. The purple overwhelmed it and I couldn't get rid of it without eliminating the fluorescent orange too. Using the new bulb and filter I got excellent results with it last week. So I'll eventually get that one posted here too.

Comstock Mine Dumps
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Amanda picks through the rocks at the base of the mine dump.
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On the last day of a camping and rockhounding trip through Northern Arizona and Southern Utah, we visited a mine dump west of Cedar City, Utah. The rock piles were immense and forbidding. But there was much to be found. The material contained a great deal of magnetite as we later discovered its effect on a compass needle. I still haven't identified a number of the clear, cream, yellow and orange crystals that adorned the stones we brought back. Several specimens turned out to be fluorescent, glowing orange, yellow and white under long wave UV. This is definitely an area I would like to pick through again.

Collection of rocks I collected at the site.
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Click image for larger version.

This stone is only mildly magnetic, giving just the slightest tug on a compass needle. Rust colored and clear crystal runs through it. The outer structure of the orange mineral is best seen in the enlarged image. A very small, turquoise colored fleck can be seen in the center of the wide image. I'm not sure if this is contamination from another stone in the rock dump or if it is native to this specimen, but we collected no other material of that color. It is yet another piece in need of testing to try and narrow down the species.

One possibility I'll look into is whether the orange/brown material is Limonite after Pyrite. The external brown form has emerging crystal forms that appear to be cubic amid striated, botryoidal features.

Click image for larger version.

Click image for larger version.

This delicately detailed pair of stones seemed a bit out of place among all the other material at the mine dump. I couldn't leave them there. A quick scan in a couple field guides suggests Dendritic Pyrolusite. However, it appears that the true mineral identity of the dendrites requires some meticulous laboratory examination...which means I'll leave this identified generically for now.

Eric Graff has been providing a lot of helpful input on the specimens I've posted so far. He notes the following about this one:

Interesting rock! My first guess would be tenorite, CuO, (the only mineral listed from Iron Springs District that is noted for the formation of dendritic patterns).

From Mindat entry on tenorite: http://www.mindat.org/min-3912.html

Morphology:Paper-thin twinned aggregates and laths parallel {100} and elongated [011] (Vesuvius); striated [010] on {100}. Curved plates. Thin shining flexible scales. Stellate groups. Earthy, pulverulent.

Twinning:1. Common on {011}, producing dovetail reentrants and feather-like forms as senn on {100}; also stellate groups andcomplex dendritic patterns. 2. On {100} ?

My second guess would be iron oxide (hematite) as I've heard that can also form dendritic patterns. While manganese oxide does frequently form these types of structures, I don't see any manganese-bearing minerals from that district.

Eric

Thanks Eric!

I'm wondering about scraping some of it off and attempting a flame test on it...

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Click image for larger version.

White Light View
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Long Wave UV View
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Amanda collected this little chunk of crystal-infused magnetite. It featured two different types of crystaline structures. The best part though was seeing it under a black light. The two different crystal types fluoresced with different colors: yellow and orange. Additionally, some less prominent material exhibited a white fluorescence. It should be interesting working on identifications for this one.

The LW Ultraviolet images can be seen below each of the white light views. Visible in the second set of images is a beautiful, thin vein of the white-fluorescing material along a less exposed edge of the stone. This was my second attempt at black light photography. It turns out to be pretty tricky. My first set of image exposed a huge amount of visible purple from the light that didn't seem as prominent visually. A lot of heavy color balance gymnastics in the camera RAW conversion process brought it back to something that was workable. Further work in the LAB color space while looking at the rock under black light was also required to take it the rest of the way.

After doing some more research, I picked up a Long Wave UV Filter from UV Systems. I also picked up an 18" black light bulb manufactured by Phillips since it apparently has a higher density of UV compared to visible emission. Placing the LW UV filter across the bulb produced a noticeable reduction in visible purple and the photographs turned out much better. I didn't need to horse around with color balance in RAW or LAB. The only issue was some of the crystal faces that reflected the light directly into the camera still possessed a purple appearance, and I needed to use the selective color filter to remove that. The images you see here are a result of that 2nd set of photographs.

White Light View
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Long Wave UV View
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Click image for larger version.

The larger crystals on this rock are about 1 cm in length.

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Click image for larger version.

This piece of magnetite possessed the largest crystals of those we found on July 21st. Although, even at that, the longest edge on any of the crystals is no more than 6 mm.

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This is one of several magnetite rocks we collected from one of the rock dumps near the Comstock Mine in Iron Springs County, Utah. I'm working on identifying the orange crystals and will update this entry when I figure it out. Below is an enlarged view.