Mohs scale of mineral hardness integrity, they are not considered "scratches" for the determination of a Mohs scale number. The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) is four times as hard as corundum. The table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate (unglazed porcelain) has a hardness of approximately 7.0. Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale. The table below
Measuring the Universe Measuring the Universe Measuring the Universe is a performance art work by Slovak artist Roman Ondak first installed in the Pinakothek der Moderne in Munich in 2007. The exhibition stars as a blank white wall and begins to fill when museum guards mark visitors' height along with their name and the current date. It is in the collection of Tate Modern in London, Pinakother der Moderne in Munich and MoMa in New York. The only items required for the installation were a white room and a few black markers. What began as a clean white space has been filled with