Do you know your sand?



I thought I knew the answer, until I thought about it a little longer.  Sand is crushed shells…….Right?  But there is sand throughout the world.  What about in deserts?  Where did all that sand come from if there are no oceans near it?


The most common source of sand in non-tropical coastal settings is silica in the form of quartz, crushed rocks.

The second most common source is calcium carbonate in the form of crushed shells, most apparent in areas that have had ocean reefs for eons.


But “sand” is also a classification of size, smaller than gravel but bigger than silt.


So, why does sand come in different colors?  It depends on the rocks that have eroded to become sand. 


Feldspar in the granite rocks near White Sands National Monument in New Mexico create the stunning white color.  Sands derived from volcanic basalts and obsidian are dark to black in color, like in Santorini, Greece. 


Some sands are green in color depending on the minerals in the surrounding rocks.  Papakolea Beach in Hawaii is also called Green Sand Beach because of the olivine in the volcanic lava.


Coral Pink Sand Dunes State Park in Utah are quartz with hematite, the mineral form of iron oxide, creating the orange color.


Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones.


Desert sand results from the fragmentation of granites, limestone and sandstone.  There is a certain critical size (about 0.5 mm) below which further weathering of rocks does not occur and this provides a minimum size for sand grains.


During a sandstorm, the wind-blown sand particles become electrically charged. Such electric fields can produce sparks and cause interference with telecommunications equipment. They are also unpleasant for humans and can cause headaches and nausea.


The color Desert Sand is a Crayola crayon color as well as a color used by General Motors as a paint color for their early Cadillacs.


The sugar-white sand in the panhandle of Florida is mainly quartz from the Appalachian Mountains, just to the north.  It has washed down to the Gulf by streams and rivers, primarily the Appalachian.


People who collect sand as a hobby are known as arenophiles and there is even an International Sand Collectors Society.   Organisms that thrive in sandy environments are psammophiles.


There you go!  Everything you have always wanted to know about sand.

Devon Higginbotham