SiO 2. One of the most common minerals in the world, quartz can be found in sedimentary, metamorphic, and igneous rocks throughout Virginia. Quartz typically appears as clear or whitish crystals within a rock such as granite.Amethyst, agate, chalcedony, chert (flint), and opal are all varieties of quartz.iO 2. One of the most common minerals in the world, quartz can be found in sedimentary, metamorphic, and igneous rocks throughout Virginia. Quartz typically appears as clear or whitish crystals within a rock such as granite.
In statistics, the standard deviation is a very common measure of dispersion. Standard deviation measures how spread out the values in a data set are around the mean. More precisely, it is a measure of the average distance between the values of the data in the set and the mean.
standard deviation. a measure of the dispersal of a random variable; the square root of the average squared deviation from the mean. For data that have a normal distribution about 68% of the data points fall within one standard deviation from the mean and 95% fall within two standard deviations. Symbol is Ï.tandard deviation (SD) the dispersion of a random variable; a measure of the amount by which each value deviates from the mean. It is equal to the square root of the variance.