Sandstone is a rock of classic origin (unlike organic elements like coal and chalk, or chemical-based elements like Jasper and Gypsum). It is formed from cemented grains that might either be fragments of some pre-existing rocks or could be mono-minerally crystals as well. The cement that binds the grains together is generally silica, clay and calcite.
The grain sizes in the sands are in in the 0.1 mm to 2 mm range and rocks and clays with smaller grain sizes, including shales and siltstones, are called argillaceous sediments. The ones with much larger grain sizes including conglomerates & breccias and are called rudaceous sediments.
What Affects The Formation Of Sandstone?
The environment where the sand is deposited is vital in determining the specific characteristics ad qualities of the resulting sandstones. In finer detail, these include its composition, grain size, and sorting and composition. In more general detail, it consists of the rock sedimentary structures and geometry. The significant environments of deposition may be divided between:
- Marine– Deltas, Tidal flats. Shoreface & Beach sands
- Terrestrial- Alluvial fans, Deserts (dunes & ergs), Glacial outwash, Lakes and Rivers (levees, channel sands, point bars) sand waves, Offshore bars and Storm deposits (tempestites) as well as Turbidites (submarine fans and channels)
The Formation Of Sandstone Involves Two Basic Stages:
- First, layers of sand accumulate as the result of the sedimentation, that occurs either from the air in desert settings or from water in sea, lakes, streams, or lakes. Typically, the deposition occurs when the sand settles out from suspension- when it ceases to be bounced/rolled along the ground surface or the bottom of a water body.
- Once all the sand has accumulated, it starts getting compacted due to the pressure from the overlying deposits. It slowly gets cemented due to the process of precipitation of minerals within the pores or spaces between the sand grains.
Calcium carbonate and silica are the most common cementing materials that are generally derived either from the alteration of the sand after it gets buried or from dissolution. The colours will usually be yellow/tan (from a blend of dark amber feldspar content in the sand or clear quartz).
For more information on which type of rock sandstone is, feel free to contact Trstone Mason at 0414 447 554 to discuss details about your project. You can also get in touch with us via this Contact Us form and get a free quote today.