Technical Info 

It is 50% uranium by mass and is a naturally forming crystal of Uranium. Natural uranium contains about 0.7% uranium-235 which is the fissionable isotope used in nuclear reactors. This sample has about 2.5 grams of autunite which translates to about 8.75mg of the same isotope that nuclear bombs are made out of! The remaining 99.3% is U-238, also known as depleted uranium. 

Uranium is a chemical element with the symbol U and atomic number 92. In its pure form, it is a silvery-grey metal but this sample is obviously not the metal form.  Uranium is part of the actinide series of the periodic table.

Most people think of modern technology when they hear the word uranium since it is the key element in nuclear energy and nuclear weapons.  However, Uranium was actually used as far back as the middle ages as a color additive to glass. 

Regulations

It is not regulated by law because it is a natural crystal specimen.  It is license-exempt and considered a Radioactive Ore Sample or Naturally Occurring Radioactive Materials (NORM). That being said, Autunite is becoming increasingly hard to find and collect. 

The cube is slightly radioactive but the acrylic shields most of the Alpha and Beta particles. Background radiation we are exposed to this every day is about 30CPM. These samples measure anywhere from 60 to 120 CPM. So about 2 to 4 times the background radiation. In comparison, you would receive more radiation flying on an airplane. X-rays at the doctors would be thousands of times this dose.  Also, a side note the FDA allows for a person to consume about 20mg of uranium in their drinking water every year.  The bottom line is that this cube is very safe unless you were somehow able to break it open and make pistachio pudding with it.