Aenigmatite

Aenigmatite is a rare silicate mineral with the chemical formula Na2Fe2+2Fe3+TiSi2O10. It belongs to the aenigmatite group of minerals, which are characterized by their complex structure and unusual chemical compositions. The mineral typically occurs as dark brown to black prismatic crystals, often appearing as aggregates. It is known for its striking appearance, with crystals sometimes exhibiting a bronzy luster. Aenigmatite is found in a variety of igneous rocks, particularly those that are alkaline or undersaturated with silica, such as phonolites, trachytes, and ijolites. It can also be found in some pegmatites and metamorphic rocks.

The name "aenigmatite" is derived from the Greek word "ainigma," meaning riddle or enigma, reflecting its complex and unusual composition which initially puzzled mineralogists. Its discovery dates back to the 19th century. Significant occurrences of aenigmatite have been reported in several locations worldwide, including Greenland, Norway, Canada, and the United States. While not a commercially significant mineral, aenigmatite is of great interest to mineralogists and geologists due to its unique crystallography and its role in understanding the petrogenesis of certain rock types. Its presence can provide valuable clues about the chemical environment and conditions under which these rocks formed.