Brief Description: From Greek term pyr (fire) and louo (wash), because it was used to clean glass from colours that were due to iron mixtures. It has the chemical formula MnO2 and it belongs to the Oxides category. Its colour is iron-black, lead-ashy or bluish and its lustre ranges from metallic, semi-metallic to dull. It is opaque and its specific gravity is 4.4 to 5.1. Its hardness ranges from 6-6½ (for crystals) and 2-6 (for granular material). Finally, its fusibility is 7. Its crystals are rarely prismatic (polianite). It usually occurs in fibrous, botryose, reniform, granular or dendritic aggregates. It is the most common manganese mineral and it connects with other oxides and hydroxides of manganese and iron, as well as rhodonite, rhodochrosite, siderite, calcite etc. It is a very important manganese ore. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/106/az_gr.htm Τσιραμπίδης Α. (2005). Ο ορυκτός πλούτος της Ελλάδας. Εκδόσεις Γιαχούδη Θεσσαλονίκη, σελ. 391. Berry, L.G., Mason, B. and Dietrich, R.V. (1983). Mineralogy. W. H. Freeman and Company, San Francisco, 561 pp.