Mineral Species: Quartz var. Amethyst

Chemical Formula: SiO2

Chemical Name: Silicon Dioxide

Mineral Class: Tectosilicates

Mineral Notes: Amethyst is a variety of macrocrystalline Quartz (SiO2) displaying shades of violet due to the presence of small amounts of Fe3+ ions. The colour is usually strongest in the crystal terminations. It is a popular semi-precious gemstone. However the colour can fade in strong light. Interestingly heating can give rise to green, yellow and brown tones.

Description: A very nice Amethyst cluster consisting of well-formed pyramidal prisms. The colour is not as deep as some forms of Amethyst, but careful examination shows the crystals to contain thread-like inclusions of Hematite. Some of these form starburst-like formations. Underneath the specimen is a thin matrix of brown quartz which has many small islands of pale green Malachite. Overall, a great little display specimen.

Location: Shaba, Dem. Republic of Congo.