Aluminite
Aluminite is a naturally occurring hydrous aluminum sulfate mineral with the chemical formula Al2(SO4)(OH)4·7H2O. It is typically found as white, earthy or chalky masses, or as fine needles in cavities. It is a secondary mineral, forming from the alteration of aluminum-rich minerals in the presence of sulfuric acid-bearing solutions.
Properties: Aluminite is a soft mineral, with a Mohs hardness of only 1 to 2. It has a low specific gravity of 1.66 to 1.83. Its luster is typically dull and earthy. Aluminite is odorless and has a slightly astringent taste. It is soluble in hydrochloric acid.
Occurrence: Aluminite is found in a variety of geological environments, including coal mines, caves, and volcanic areas. It commonly occurs in association with other sulfate minerals such as gypsum, alunogen, and epsomite. Notable occurrences include Halle, Germany; Montmartre, France; and various localities in the United States.
Uses: Aluminite has limited industrial uses. Historically, it has been used as a source of alum and in the manufacture of paper. It is primarily of interest to mineral collectors and researchers.
Identification: Aluminite can be identified by its white color, soft nature, occurrence in sulfate-rich environments, and chemical tests. X-ray diffraction analysis provides a definitive identification method.