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
Schiehallion including dog's mercury, lily of the valley and wood anemone. The majority of Schiehallion consists of Quartzite, a rock formed from an original sand by heat and pressure. Quartzite is a white or pinkish rock, in which the dominant mineral is Quartz. Quartz is hard, being number seven on the Mohs scale of mineral hardness. It is able to scratch glass since it is harder than glass. People often mistakenly think that Schiehallion is an extinct volcano because its shape is reminiscent of an active volcano. If fact it formed by sedimentary processes and the shape is the result of