Type of Rock Sedimentary Rock: Gypsum

Photo and sketch of rock
Rock Identification Gypsum rock have inconsistent jiggered surface. Gypsum rock are made up of gypsum mineral and pure gypsum rock are white in colour. However, some impurities that combined together to form gypsum rock may give different colours to the rock.
Description of gypsum:
Type Name Cleavage Colour Lustre Hardness Specific Gravity
M456 Gypsum Have cleavage White or grey in colour Vitreous to silky 2 2.33
Characteristics Features and Physical Properties Gypsum is a soft and light mineral that moderately soluble in water. Gypsum is usually white or grey in colour but sometimes it can also be found in shades of green, pink, yellow and brown due to presence of impurities. Gypsum crystal is flexible but they are not elastic
Mode of Formation and Occurrence Rock gypsum formed when concentrated solutions like seawater evaporated. Hence gypsum rock are abundant at places with high evaporation rate such as at desert lakes and marine region. Formation of gypsum crystals that formed at desert is known as “desert rose” formation as it resembles petals of flower
Similar rocks and minerals Gypsum is sometimes confused with anhydrite. Both gypsum and anhydrite share an approximate appearance which is they are commonly exist in white colour.
Gypsum can be related to bassanite in term of chemical composition. Both gypsum and bassanite contain hydrous calcium sulphate, however, gypsum(CaSO4·2H2O) contains more water compare to bassanite (CaSO4·0.5H2O)
Gypsum is widely used manufacture of wallboard, cement, plaster of Paris, soil conditioning, and a hardening retarder in Portland cement. Usage of gypsum in construction is rather wide due to its eco-friendly properties. Study shown that gypsum construction products have enhance properties in flexure and thermal conductivity.

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Type of Rock Sedimentary rock: Shale

Photo of shale Sketching of shale

Rock Identification Shale rock is the most abundant sedimentary rock on Earth. It have laminated appearance and usually formed in sheets. Shale is also one of the fine-grained rock and consists of silt and clay sized particles. Shale are made up of 30% clay, minerals and large amount of quartz. It also have small amount of carbonates, feldspar and organic matters

Description of quartz:
Type Name Cleavage Colour Lustre Hardness Specific Gravity
M286 Quartz Indistinct No colour Vitreous 7 2.65
Characteristics Features and Physical Properties Shale have tendency to break into thin layers which usually will be parallel to plane surface. Shale also have properties of plasticity and permeability. Shale have very tiny pores known as nanopores inside its structure. Shale will have darker colour when the organic content in it is high. Hematite and limonite will make shale to appear reddish and purple in colour.
Mode of Formation and Occurrence Shale forms as a result of compaction and cementation of materials that eroded from pre-existing rocks. Compaction and cementation of clay minerals and silicates will eventually form shale. Shales are usually deposited and can be found at places with very slow flowing water such as lakes, river deltas, and sedimentary basins.

Similar rocks and minerals Most of the time, shale are being confused with slate. Both stone have very little difference in terms of appearance and one cannot directly distinguish these two type of rocks by just visually examined it. Slate is metamorphic rock that formed from shale that exposed to pressure and heat.

In terms of mineral similarity, shale can be related to schist. Schist is a metamorphic rock that formed through metamorphosis process. Study revealed that schist parent rock was shale which mean shale rock that undergo metamorphosis will end up become schist. Since schist was once shale rock, their mineral composition is almost the same.

Shale are commercially used for applications in the ceramics industry. Shale are very important raw material to manufacture tile brick and pottery. Organic-rich shales known as oil shales that contain kerogen(a complex mixture of solid hydrocarbons derived from plant and animal matter) are currently being study to turn it into practical source for liquid petroleum