This piece is a Selenite Floating Cube with optical quality. It measures approx. 39 x 39 x 39 mm in size and weighs approx. 125 grams. This piece only, will come with a light stand. 
 
Selenite is a variety of gypsum. Selenite's Mohs is a 2; it is found in the USA and Mexico. If can react to Low Wave UV spectrum and will turn yellow. Optical qualities means you can view objects thru the Selenite to point that they are clear and somewhat projected (magnified).