Rock Crystal. See [Quartz].
Rock Gypsum. See [Gypsum].
Rock Salt. See [Halite].
Rose Quartz. See [Quartz].
Salt. See [Halite].
Sand and Sandstone
[Sand] is a loose, uncemented [sedimentary] deposit made up of fragments of weathered rocks and minerals. These fragments must be of a certain size (between ¹/₁₆ millimeter and 2 millimeters in diameter) in order to be called sand grains. The largest sand grains are about the size of a pinhead. Sand grains are smaller than the fragments known as [granules]; they are larger than those known as silt.
Many sands are made up chiefly of grains of [quartz]. This mineral is plentiful and does not easily weather away. In addition, rock fragments and many other minerals, such as [feldspar], [mica], [gypsum], [magnetite], and [garnet], are found as [sand] grains.
Rains wash many of the [sand] grains and other weathered rock and mineral fragments into creeks and rivers. These streams may carry the sand and other [sediments] long distances before depositing them. Today, we find sands along the banks of many creeks and rivers in Texas and along the beaches of the Gulf of Mexico. The sand in the rivers is in transit to the Gulf. In addition, sand occurs at the surface in other [Cenozoic] [formations] and in some of the [Paleozoic] and [Mesozoic] formations of Texas.
[Sand] has many uses. Much building sand, which is used in mortar and concrete, is produced from numerous sand and [gravel] pits in Texas. Pure [quartz] sand that can be used to make glass is known as glass sand. Some of it is found in north-central Texas in Lower [Cretaceous] [formations]. A large glass sand quarry is located at Santa Anna in Coleman County. Along the [Gulf Coastal Plain], sand that is used in glassmaking occurs in [Eocene] [Tertiary] strata.