Sunstone is a variant of the Feldspar mineral - which is chiefly Silica based with either Potassium, Sodium or Calcium making the rest of the mineral and in fact, this variant is Sodium Calcium Aluminium Silicate.

With a range of 6.5- 7.2 on the Mohs Hardness Scale, it's quite a hard mineral and the colours are due to reflections from the inclusions of minute amounts of red copper inclusions  which allow colours from clear, through yellow, red, green, and blue.

Sunstone has been chiefly found in Southern Norway and some parts of the United States.

Some examples of sunstone are shown below.