I apologize for the poor image quality, but with the holiday season here I really don't have room to set up my photography area in order to get a nice, clear picture. In addition, my camera has been having trouble taking non-blurry pictures lately.
When I first got the potassium it was kept under oil in a standard screw top jar. My sample was cut from a larger sample which already had a pretty thick oxide layer on it, but when mine was cut it had a fresh, clean surface to it. Over time, this surface slowly oxidized and became a semi-transparent white color. (I could tell it was oxidized, but I could still see some metal through it). I also noticed that over time some parts at the corner of the cut surface started to turn orange/brown which is a sure sign of peroxide/superoxide formation. That kind of sucked. As a result, I went and decided to get a different container for it.
I got the jar from a buddy of mine who had purchased a large quantity of them and transferred my potassium to it. I surrounded the threads with Teflon tape and then tightened the seal on the jar as tight as I could. The inside of the jar was filled to the top with mineral oil to reduce the available air space in there too. With the lid tightly sealed, I then wrapped some electrical tape around the outside edge to provide another barrier. I may in the future find another alternative, but the electrical tape conforms to curves very well.
Anyway, when I had the potassium out in the open I went and excised one corner which had a very large growth of superoxide on it. I took a razor blad and just cut apart the bad section and chucked it in some water. I then put the potassium in the oil and sealed it. Over time, I noticed something odd. In the corner I had cut and in another corner where bare metal was exposed, it was starting to turn colors. The thing is, the red-orange color was NOT the same type of color as the oxide/peroxide. Instead, it looked like an anondized type red. This was puzzling to me because I don't know of ANY potassium and nitrogen/oxygen/anything else compounds that are this red. (At least not anything that would be a viable option here). What I then began to notice was the parts of the potassium which had a heavy superoxide crust on it weren't as heavily encrusted anymore. I was also able to see a better metallic sheen to the oxidized parts.
Then, after reading a post by woelen in regards to niobium metal, I realized that there must be a very, VERY thin layer of oxide on the potassium which is resulting in the bending of the wavelengths of light. What must have happened is that the jar has become sufficiently air-tight so that no more oxygen is able to get in. Whatever is in there has already reacted so there is no more to thicken the oxidization of the bare metal, thus why the red color can remain. The drop in the presence of the peroxide/superoxide could be the result of the stuff decomposing slowly over time as well. It really has thrown me for a loop. When I get my photography setup taken care of, I'll try and post a better picture of it.