a smooth black rock that they found in the Cedar river, It feels rather heavy. Y

Question

a smooth black rock that they found in the Cedar river, It feels rather heavy. You can see that whatever minerals or rocks it is made from are far too small to see with the naked eye. Describe how you would make your own scientific identification of the rock. End the description of your scientific method with the name of this rock.

- Describe the texture, composition, and the environment of formation of conglomerate.

-Explain all the ways that sandstone and limestone are different from each other.

Explanation / Answer

The given rock happens to be smooth black rock,and is too dense ,from the given observations it can be said that the rock could be a fine grained hematite bearing or hematite-magnetite bearing rock.It could be a part of a larger banded iron formation or could be a part of a placer deposit of basalts(igneous rock).The rock could be identified by noting the minerals present. The observer could check for the streak,if its cherry red in color, the rock may contain hematite,magnetite can identified by its magnetic property.

Conglomerate is a type ofsedimentary rock that is composed of large, rounded rock fragments contained within a smaller grained matrix of sediments. The large fragments, known asclasts, can come in a range of sizes, but all must be greater than two milimeters in diameter in order for the rock to be classified as a conglomerate.

The texture ofconglomerates are defined as being composed of round pebble or cobble sized grains in a finer matrix

The rock is usually composed of quartz, feldspar,clays,calcite and mica's.

The conglomerates form in sedimentary environments namely of fluvial,glacial and oceanic origin.

Sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, gray and white. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions.
The usual cementing material in sandstone is calcium carbonate, iron oxides, or silica, and the hardness of sandstone varies according to the character of the cementing material; quartz sandstones cemented with quartz are the hardest.In sandstones, sand is between 1/16 millimeter and 2 mm in size (silt is finer and gravel is coarser). Sandstone may include finer and coarser material.
Sandstones are classified on the basis of the composition of their grains. Three components are considered:

Quartz grains
Feldspar grains
Rock fragment grains

Based on the percentage composition of these components, the color and the physical properties of the various varieties of sand stone varies.
Physical Properties of Sandstone
The physical properties of sandstone includes following:
Mineralogy:
A wide variety of rock fragments with up to 75% quartz grains .
Texture:
Medium-grained; may range widely in degrees of grain sorting and shape.
Structure:
Bedding is often apparent along with sedimentary structures and fossils
Occurrence:
Associated with most other sedimentary rock types .
Color:
The color varies from red, green, yellow, gray and white. The variation is result of the binding material and its percentage constituent.
Water Absorption:
The capacity of water absorption is not more than 1.0%
Porosity :
The porosity varies from low to very low.
Density:
2.32 to 2.42 Kg/m3
Hardness:
Lies between 6 to 7 on Moh's Scale
Compressive Strength:
Varies from 365 to 460 Kg/m2
Chemical Properties of Sandstone
Constitutent                              Percentages
Silica (SiO2)                              93-94%
Alumina (Al2O3)       1.4-1.5%
Iron (Fe2O3)                             1.5-1.6%
Lime (CaO)                               0.8-0.9%
Soda (N2O) & Potash (KrO)   1.0-1.2%
Magnesia (MgO)                     0.2-0.25%
Loss of Ignition (LOI)              1.0-1.2%
They are highly resistant to acids, alkalis and thermal impact and their insolubility in acids and alkalis is about 97%
Uses of Sandstone
Sandstones are used for variety of purposes. They are mainly used in paving, roofing, flooring etc. They are also used in making beams, pillars, doors and window sills, wall facing, fence posts etc.
Sandstones are resistant to saline air, which make it perfect for exterior cladding in sea-shore buildings.
They are also acid and alkali resistant. So, they are used in chemical industry for flooring, wall-covering.
They are thermal resistant so used for making fireplaces.

Limestone

Limestone is ca alcareous sedimentary rocksformed at the bottom of lakes and seas with the accumulation of shells, bones and other calcium rich goods. It is composed of calcite (CaCO3). The organic matter upon which it settles in lakes or seas, are preserved as fossils. Over thousands and millions of years, layer after layer is built up adding weight. The heat and pressure causes chemical reaction at the bottom and the sediments

The rock which contain more than 95% of calcium carbonate is known as high-calcium limestone.Recrystallised limestone takes good polish and is usually used as decorative and building stone.
A part of calcium molecules if being replaced by magnesium, it is known as magnesium lime stone or dolomite limestone.
Limestone that will take a polish are considered marbles by most people, but technically, if there are still shells visible or the structure is not crystalline, it is still a limestone.
Physical Properties of Limestone
Hardness 3 to 4 on Moh's Scale
Density 2.5 to 2.7 Kg/cm3
Compressive Strength 60-170 N/mm2
Water Absorption Less than 1%
Porosity Quite low
Weather Impact Resistant
Chemical Properties of Limestone
Constituent                                Percentage
Lime (CaO)                              38-42%
Silica (SiO2)                             15-18%
Alumina (Al2O3)    3-5%
MgO                                         0.5 to 3%
FeO + Fe2O3                           1-1.5%
Alkalies                                    1-1.5%
Loss On Ignition (LOI)    30-32%
Uses of Limestone
• Flooring
• Wall cladding
• Vanity tops
• Furniture
• Cement Production
• Refining Metals
• Blackboard chalk
Comparison
Sandstone and limestone both are sedimentary rocks but sandstone is formed by the sedimentation of small grains, usually quartz (silica). The individual grains are visible and vary form small to large size. While limestone is formed by the sedimentaion of finer grains of calcarious materials. As limestone is composed of finer grains so its density is more as compared to that of sandstone, and so pores in the sandstone are more Limestone, like marble and other calcareous stones, are referred to as acid sensitive. Calcareous stones are readily dissolved in acid, while sandstone do not react with the acids. Limesotne is generally soft, and can be corroded by rainwater. Sandstone is hard as compared to limestone and less corroded by rainwater, so we find it near the rivers, lakes and in desert areas.
Sandstone is preferred for the use in metallic road construction because its hardness, compressive strength is more. It is more resistant to the weathering by rainfall and can not be corroded easily by rainwater. So, at different climatic, water and weather conditions sandstone is better construction material.
Limestones are responsible for the typical Karst topography.

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