Icelandite is a very specific sub-variety of andesite, a volcanic rock associated with basalt. It is found near the mid-Atlantic ridge that runs through Iceland.
Icelandite has the distinction of being called the "closest thing on Earth to the rocks found at the (Mars) Pathfinder landing site".
Take a look again at the pictures of Mars taken during the Pathfinder mission...there's Yogi, Barnacle Bill, Stimpy, Flattop and the whole rocky gang...and they all have chemistry that most resembles this sample!
Specimen Size: 42mm H X 27mm W X 21mm D, 34 grams
Specimen is presented in a 2-inch hinged perky.
Bet you do not have this one yet in your collection! Very rare.