Larvikite

This, as the header of this post suggests, is Larvikite.  You've probably seen it cladding buildings and sparkling in the sun.  It is an intrusive igneous rock - one that is formed from magma that solidified underground. In this case, this happened near what is now Larvik (hence the name) in Norway.

Larvikite is similar to granite in many ways but it has far less quartz than granite has. The feldspar minerals are iridescent because of some rather cool optical interference, rather like a kingfisher's feathers, and the iridescence varies as the angle you're looking at it from changes.  A polished slab is a so-and-so to photograph because the camera just looks through it to your reflection and you wind up with a selfie.* You also see it used in large, unpolished, blocks as coastal defences, and it's still very much worth a close look then.

Incidentally, a chap by the name of Sir Montague Maurice Burton (of menswear fame) used Larvikite on the outside of his premises  in an early example of corporate branding; some geologists do still "amusingly" refer to it as 'Burtonite'.

*I counted myself very lucky to get this photo. I finally managed it with a new phone(!), one of the cheaper Samsung ones.