Mineral Species: Tourmaline var. Schorl

Chemical Formula: Na(Mg,Fe,Mn,Li,Al)3Al6(Si6O18)(BO3)3(OH,F)4

Chemical Name: Sodium Aluminium Borosilicate

Mineral Class: Cyclosilicate

Mineral Notes: Tourmaline is actually a misnomer, describing several closely related, but chemically different, minerals. The variety Schorl is a tourmaline species rich in iron and managenese, which give rise to the dark colouration. Tourmalines are highly sought-after gemstones particulalry when the colour changes along the length of the crystal due to changes in composition during growth. 

Description: A doubly-terminated, hexagonal crystal of Scholr on matrix. One termination is a simple hexagonal pyramid, whilst the other is complex and contains a matrix inclusion. There are numerous other individual and integrown crystals on the matrix. The tourmaline has an intense black colour and vitrous luster. The contrast between the black mineral and underlying white matrix is very attractive.

Location: Sahatany Pegmatite Field, Vakinankaratra, Antananarivo, Madagascar