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
Mineral Point, Wisconsin county seat of Iowa County was relocated to nearby Dodgeville, Wisconsin, where it remains today. Afterwards there was an intense rivalry between the two cities, during which Mineral Point fired a cannon towards Dodgeville's direction. As lead mining declined in Mineral Point, zinc mining and smelting became important new industries. Zinc ore was discovered with increasing frequency near the bottoms of old lead mines. The Mineral Point Zinc Company was founded in 1882, and by 1891 it was operating the largest zinc oxide works in the United States at Mineral Point. Zinc mining and processing continued on a large scale