Tag: rocks

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.

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.

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.