Mineral necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others. An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100]. The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below: Lustre indicates how light reflects from the mineral's
Universalmuseum Joanneum collection traces its origin to the private collection of Archduke Johann, which encompassed several thousand pieces at that time. Today the inventory has grown to about 80,000 specimens. The collection presents minerals from across the world as well as a Styrian regional collection. The mineralogy department of the Joanneum was where Friedrich Mohs developed the Mohs scale of mineral hardness which remains authoritative. He was the first curator of the Joanneum. Schloss Eggenberg was added to the registry of the Graz Old Town as a UNESCO World Heritage Site in 2010. Schloss Eggenberg is the most significant palace ensemble in