Sandstone Handicrafts

Sandstone is a type of sedimentary rock. It is made up of particles of preexisting rocks and minerals. These particles are usually igneous rocks, metamorphic rocks or even other sedimentary rocks.

Sandstones are originally clastic. They are generally found under seabed, riverbed, or under desert areas. Under the influence of some type of current (wind, waves, flowing water, or glacier) the layer of particles starts depositing one above another. They are composed of fragments or particles of older rocks or previously existing solid matter. The cement binding these grain are especially silica, calcites and clays.

Formation
The formation of sandstone involves two primary stages. At first, due to sedimentation, a layer or layers of sand accumulate either from air (in deserts) or from water (in rivers, lakes, sea). Sedimentation occurs by settling of sand grains down the bottom of seabed, riverbed or, on the ground surfaces. This process of sedimentation continues to hundreds or thousands of years. Gradually thick layers of sand deposits one above another. Slowly and steadily, the upper layers exerts pressure on lower layers. Other external agencies, like water (in river, sea) and air, also exerts pressure on these layers. Due to these external effects and pressure of overlying deposits, the sand consolidate and changes in sandstone. It is cemented by the precipitation of minerals within the pore spaces between sand grains. Silica and calcium carbonate are the common cementing materials.

Classification Based on Grain Size
The sand grain size covers the range 0.1 mm to 2 mm.

• Argillaceous: The rocks with smaller grain size includes shales, clays and siltstone and are typically called Argillaceous sediments.
  
  
• Rudaceous: The rocks with larger grain size includes Breccias and conglomerates and are known as Rudaceous sediments.

The characteristics of the resulting sandstone, like grain size, color, sedimentary structures etc. is largely determined by the environment where it is deposited.

Occurrences of Sandstones
Rajasthan is the largest producer of sandstones in India. Dholpur, Chittorgarh, Jaiselmer, Jodhpur, Bikaner, Kota, Bhilwara are some of the important places in Rajasthan where sandstones are found in abundance. In Madhya Pradesh, Gwalior is the main place where sandstones are present.

In India sandstones are mainly found in states including:

• Rajasthan
• Madhya Pradesh
• Chhatishgarh
• Himachal Pradesh

Outside India, it is mainly found in Scotland and Algeria.

Physical Properties of sandstone

• Color- Different varieties of colors are available like red, yellow, white, pink, gray and many more.
• Hardness- On moh's scale its density lies between 6 and 7.
• Comprehensive strength- It is usually between 360 to 465 kg/m2 u
• Porosity- Usually porosity is very low.
• Density- 2.30 to 2.41 kg/m3
• Water absorption- The water absorbing capacity is up to 1% only.

Chemical properties of sandstones:
The chemical constituent of sandstone is same as sand. It is mainly made of quartz. The cementing constituent that binds it together is usually silica, calcium carbonate, and iron oxide. Sandstones are vastly resistant to alkali, acids, and heat.
Constituent of sandstone by percentage :

Silica (SiO2):	91% to 93%
Alumina (Al2O3):	1.3% to 1.45%
Iron oxide (Fe2O3):	1.4% to 1.55%
Soda and potash:	1.0 % to 1.2%
(NaO & KO2)
Lime(CaO):	0.7% to 0.9%
Magnesia(MgO):	0.22% to 0.25%