geotech.docx

Name: Sandstone,

Type: clastic sedimentary rock.

Sample properties

Mineralogy: Sandstone is usually up of mostly quartz. But it can also include minerals like

hematite, ilmenite, feldspar, amphibole and mica with small quantity of clay, silts and small rock

fragments. They are always bonded together by any of these three natural cements: silica,

calcium carbonate and iron oxide.

Occurrence: Sandstone is formed as a result of sediments deposited on the Earth’s surface by

water, ice, or wind. The sand and pebbles that make up this sandstone are fragments that came

from older rocks. The fragments were carried downhill by rivers and streams millions years ago,

deposited in layers, and then bound together by natural cement.

Colour Various colours

Hardness 6 – 7

Streak Colourless or white

Cleavage None

Lustre Dull

Grain size 0.06- 2mm

Fracture Conchoidal

Tenacity Brittle

Magnetism None

Acid reaction Effervescence

Feel Rough

Crystal system None

Specific gravity

2.2 – 2.8

http://geology.about.com/od/minerals/a/aboutquartz.htm

Structures: Sandstone structures are always Cross bedded, this happens as wind, water or ice

deposits new sediments on already existing layer of rocks. This sediments with time and other

will factors will then turn to new rocks forming another layer.

Weathering: Sandstones can be affected by physical and chemical weathering. They easily

breakdown but this solely depends on the mineral composition of the cement holding the grains

together. Calcite is generally stronger than any other natural cement. Apart from the cement

holding these minerals together, the fact that sandstone layers are cross bedded makes it liable

for it to crack along its bedding planes.

1.3 CIVIL/GEOTECHNICAL ENGINEERING PROPERTIES:

Foundations: If sandstone is found on site, it can be built on. According to Ward-harvey (2009)

for domestic buildings, sandstone can provide a very good foundation. Therefore, if sandstone

was found on site which is going to use for a domestic building, there will be no need for

excavation of the sandstone. But for larger project, it can be excavated to in other to avoid

shallow foundations. The excavated sandstone can be used for building and decorative finishing

purposes. Therefore excavated material is not to be disposed.

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa

UCS saturated MPa

Modulus of elasticityGPa

Tensile strength MPa

Shear strength MPa

Friction angle

2 - 2.6 5 - 25 4 -25 8 - 40

Hydrology: Sandstones can be classified under unconsolidated sediments. Generally,

unconsolidated sediments form a very good aquifer. Aquifers formed in unconsolidated

sediments may vary, but its setting is undoubtedly the most successful in providing ground.

Hence, Aquifer is productive with diffuse flow. ('Fractured Rock Aquifers'. N.p, 2015.)

Value: Sandstone is very valuable in the construction industry. It can be excavated and used for

construction purposes and it can also be refined into beautiful looking wall and floor finishes for

buildings.

Name: Granite

Type: Intrusive igneous rock

Sample properties

Mineralogy: Granite is a plutonic igneous rock found to be mostly common in mountainous

areas. Granite is made up of coarse grains of quartz (10-50%), potassium feldspar, and sodium

feldspar. These minerals make up more than 80% of the rock. Some other minerals commonly

present includes mica (muscovite and biotite) and hornblende. Granite has about 70-77% silica,

11-13% alumina, 3-5% potassium oxide, 3-5% soda, 1% lime, 2-3% total iron, and less than 1%

magnesia and titania to be its chemical composition. ('Granite'. N.p, 2015.)

Occurrence: Granite is an intrusive igneous rock. This means that in the process of the

formation of granite, the molten magma does not get to the surface of the earth and the lava gets

cold slowly and at temperature greater than the temperature of the surface of the earth which

makes the granite to have coarse grains.

Colour Grey, pink, white.

Hardness 6 – 7

Streak Colourless or white

Cleavage None

Lustre Dull

Grain size 5.7- 11.6mm

Fracture None

Magnetism Slightly magnetic

Acid reaction None

Feel Gritty

Crystal system None

Specific gravity 2.6 - 2.7

Weathering: Breaks down into little pebbles and stones.


Foundations: Very strong material, good for making concrete and certainly for foundation

purposes. If granite was found on site, it can be built on. But it the case of high rise buildings, in

other to avoid shallow foundation, it is advisable to excavate the granite. The excavated granite

can be used for building purposes or it can be refined and used to decorative kitchen finishing.

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa

UCS saturated MPa



Shear strength MPa

Friction angle

2.6-2.9 0.5-1.5 20-50 7-25 14-50 15-20

Hydrology: Granite is a characterised crystalline rock. Their primary permeability is very low

i.e. (nearly no amount of water can penetrate the rock itself). However, water can be transmitted

through cracks and fractures which is as a result of folding and faulting of the rock due to time.

These fractures create "secondary" permeability. Aquifers which rely on secondary permeability

generally have a much lower capacity to transmit water. ('Fractured Rock Aquifers'. N.p, 2015.)

Value: Granite is of a great value in the construction industry, it may be very common but it

quite special because it can be used for both construction and decorative purposes.

Name: Quartz crystal

Type: Silicate Mineral

Sample properties

Mineralogy: quartz is basically made up of silicon and oxygen with the formula SiO2.

Occurrence: quartz is made up of silicon and oxygen. Quarts is formed when silicon in the earth

crust combines with oxygen. Quartz contains crystal lattice for that reason, it does not need a

specific temperature or pressure to form.

Structures: Quartz crystal structure is very complicated. It is formed as hexagonal prism with

modified crystal faces.

Colour

Colourless to various

colours

Hardness 7

Streak white

Cleavage None

Lustre Vitreous

Fracture Conchoidal

Tenacity Brittle

Magnetism None

Acid reaction None

Feel Smooth

Crystal system Trigonal


Taste

None

Weathering: quartz is resistant to physical and chemical weathering.


Foundations: quartz is one of the most common mineral, it is present in almost every rock.

Some of quartz based rocks are good for foundation some are not.

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa



Shear strength MPa

Friction angle

2.65 0.1-0.5 10-30

22 1.8-7 10-30 20-60 50-60

Hydrology: quartz is a crystal, for that reason it has very low or no porosity. Quartz cannot transport water because of its inability to absorb water.

Value: It can be used as a gem stone and for other decorative purposes.

Name: Olivine

Type: Silicate Mineral

Sample properties

Mineralogy: Olivine is made up of Magnesium iron silicate. ('Olivine: The Mineral Olivine,

2015.) States that “the series ranges from the magnesium end member, Forsterite (Magnesium

silicate), through the intermediary member, Olivine (also known as Chrysolite), to the iron end

member, Fayalite (Iron silicate)”.

Occurrence: Olivine is a naturally occurring rock forming mineral mostly found in dark

coloured (mafic and ultramafic) igneous rocks such as basalt, gabbro, dunite, diabase,

and peridotite. Olivine crystals can sometimes be formed during the metamorphism of

a dolomitic limestone or dolomite. The dolomite contributes magnesium, and silica is obtained

from quartz and other impurities in the limestone. (King, Hobart. 2015)

Structures: According to (Bragg and Brown, 1926) The basic structure of olivine is a close

packing of oxygen with Mg and Fe occupying one half of the distorted octahedral interstices,

known as M 1 and M 2 sites, and Silicon occupying one-eighth of the tetrahedral interstices

Weathering: Olivine is one of the weak common occurring minerals on the surface of the earth

in accordance with the Goldich dissolution series. It weathers to iddingsite (a combination of

Colour Olive green

Hardness 6.5 - 7

Streak Colourless

Cleavage Poor

Lustre Vitreous

Grain size None

Fracture Conchoidal

Tenacity Brittle

Magnetism None

Acid reaction Soluble in HCl

Feel Smooth

Crystal system Orthorhombic

Specific gravity 3.2- 3.4

clay minerals, iron oxides and ferrihydrites) readily in the presence of water. (Kuebler et all.

2003)


Foundations: If found on site, it can be built on. It can be excavated for its value as a gemstone.

Hydrology: Olivine is crystalline therefore it is not permeable which makes it to lack thbility to

transport water.

Value: It can be used as an ornament.

Name: Pyrite

Type: Non-silicate Mineral

Sample properties

Colour Pale brass-yellow

Hardness 6 - 6.5

Streak Greenish-black

Cleavage None

Lustre Metallic

Grain size None

Fracture Conchoidal

Tenacity Brittle

Magnetism Magnetic after heating

Acid reaction Melting

Feel Smooth

Crystal system Isometric


Mineralogy: pyrite is basically an Iron sulfide but can sometimes contain small amount of

cobalt, nickel, silver, and gold.

Occurrence: Pyrite occurs in hydrothermal veins as an accessory mineral in igneous rocks,

magmatic segregations and as very large bodies. It also occurs in metamorphic rocks,

sedimentary rocks as diagenetic replacements, contact metamorphic deposits and pegmatite.

('Pyrite - Occurrence, Properties and Distribution' 2015).

Structures: “Pyrite's structure is analogous to galena's structure with a formula of PbS. Galena

though has a higher symmetry. The difference between the two structures is that the single sulfur

of galena is replaced by a pair of sulfurs in pyrite. The sulfur pair are covalently bonded together

in essentially an elemental bond. This pair disrupts the four fold symmetry that a single atom of

sulphur would have preserved and thus gives pyrite a lower symmetry than galena”.

(Mineralszone.com, 2015)

Weathering: When exposed to air and water, pyrite breaks down releasing a lot of sulphur and

iron compounds.


Foundations: Pyrite is not good for foundation purposes. If found on site, it should be excavated

for its value in the chemical industry.

Hydrology: The fact that water actually attacks pyrite causing it to weather, pyrite’s ability to

transport water is very poor.

Value: Pyrite is used in the manufacture of sulphuric acid and sulphur dioxide which can be used

in the paper industry.

Name: Marble

Type: Non-foliated Metamorphic Rock

Sample properties

Mineralogy: It is composed primarily of the mineral calcite (CaCO3) and usually contains other

minerals such as: clay minerals, micas, quartz, pyrite, iron oxides and graphite (King,

Hobart.2015)

Occurrence: Marble is a metamorphic rock that occurs when limestone is subjected to a very

high temperature and pressure. Marble occurs in these conditions because the calcite forming the

limestone recrystallizes to form a denser rock consisting of roughly equigranular calcite crystals.

Structures: Marble often occur interbedded with other metamorphic rocks such as schist, gneiss

etc.

Colour Various

Hardness 3 – 4

Streak White

Cleavage None

Lustre Metallic

Grain size Medium

Fracture Conchoidal

Tenacity Brittle

Magnetism Very low magnetism

Acid reaction Fizz

Feel Smooth

Crystal system Trigonal


Weathering: Marble can be affected by natural weathering agents, but marble is mostly affected

by acidic water or rain. Marble will deteriorate when it comes in contact with even mild acid

because of its high calcite content.


Foundations: marble is generally a building stone. Its aggregate can be used for concrete

foundation, should be mixed with other strong aggregates.

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa



Shear strength MPa

Friction angle

2.6-2.7 0.5-2 7-20 14 55 7-20 0.06-0.44 35-50

Hydrology: Marble has a very tight crystalline structure as a result of this, it has a very low

porosity. Due to the fact that marble has a very low porosity, it is not able to transport water.

Value: Marble is very valuable in the construction industry, it is better used as a decorative

finish in buildings.

Name: Gneiss

Type: Foliated Metamorphic Rock

Sample properties

Mineralogy: Most gneiss rocks contain bands of feldspar and quartz in an interlocking texture.

Occurrence: It is formed by the metamorphism of granite or sedimentary rocks. Gneiss forms

when pre-existing rocks recrystallizes under high temperature and pressure. The rock remains

completely solid during metamorphosis and pressure is usually anisotropic, which then leads

to the formation of new minerals.

Structures: Most times, gneiss is always foliated

Weathering:

Breaks down into little pebbles and stones.


Foundations:

Very strong material, good for making concrete and certainly for foundation purposes.

Colour Various

Hardness 6.5 – 7

Streak None

Cleavage None

Lustre Waxy

Grain size Medium to coarse

Fracture Conchoidal

Tenacity Brittle

Magnetism None

Acid reaction None

Feel Rough

Crystal system None

Specific gravity 2.6 – 2.9

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa

UCS saturated MPa



Shear strength MPa

Friction angle

0.5-1.5 2.8-3.0 73-

340

159 58 13-23 5-20 NA 30-40

Hydrology: It is a crystalline rock. Therefore, it does not have good aquifer.

Value: Gneiss is very valuable in the construction industry, it can be used in building pavements,

cemetery monuments, dimension stone etc.

Name: Slate

Type: Foliated Metamorphic Rock

Sample properties

Colour Various

Hardness 3 – 4

Streak None

Cleavage Slaty

Lustre Dull

Grain size Microscopic grains

Fracture Conchoidal

Tenacity Brittle

Magnetism None

Feel Rough

Crystal system None

Specific gravity 2.7 – 2.8

Taste None

Mineralogy: Slate is basically made up of quartz and muscovite or illite alongside with biotite,

chlorite, hematite and pyrite. Sometimes, it also contains apatite, graphite, magnetite, tourmaline

or zircon as well as feldspar.

Occurrence: Slate is a foliated metamorphic rock derived from the metamorphism of shale. It is

formed by regional metamorphism from tectonic plates colliding with one another. (Minerals

Education Coalition,. 'Slate'. N.p., 2015)

Structures: Slates are characterized by a single, perfect cleavage (slaty cleavage), enabling it to

be split into parallel-sided slabs. On the cleavage surfaces sedimentary structures such as

bedding and graded bedding can often be seen. Fossils may be preserved but are invariably

distorted. Folds are often apparent in the field. ('Rock Types - Slate'. N.p., 2015)

Weathering: Slate is an extremely strong rock when it comes to weathering. It is sometimes

considered to be weather resistant.


Foundations:

Slates possess great tensile strength and durability. But it is not usually used for making

foundation but rather, it is used as a roofing material.

Rock strength:

Densit

y dry

t/m3

Porosit

y %

Dry

UCS

rang

e

MPa

Dry

UCS

mea

n

MPa

UCS

saturate

d MPa

Modulu

s of

elasticit

y

GPa

Tensile

strengt

h MPa

Shear

strengt

h MPa

Frictio

n angle

0.1-0.5 2.6-2.7 7-20 15-30

Hydrology: For the fact that is used for roofing, proofs its ability to resist water. Slate has little

or no ability to transport water.

Value: It is valuable in the construction industry. Shale plates can be used for roofing and its

aggregate can be used as alternatives for granite aggregates and other construction stones.

NAME/TYPE: Basalt, Extrusive rock, igneous rocks

SAMPLE PROPERTIES:

Mineralogy: basalt is generally made up of pyroxene (augite), plagioclase and olivine, possibly with minor glass; if porphyritic the phenocrysts will be any of olivine, pyroxene or plagioclase.

Occurrence: Lava flows in bedded sequence. Cooled after flowing from volcano.

Structures: Sheets or lenses. Maybe interbedded with ash or tuff. Young lavas have smooth pahoehoe or clinkery as surfaces. Compact basalt may have columnar jointing (from cooling contraction)

Weathering: Rust and decays to clay soils. Maybe spheroidal weathering.

Colour Grey, BlackHardness 2.3Streak WhiteCleavage Perfect Lustre MetallicGrain size Fine grainedFracture EvenTenacity High elasticityMagnetism Magnetic

Acid reactionReacts with acid

Feel Rough solidCrystal system ClinopyroxeneSpecific gravity 2.8 – 3.0

CIVIL/GEOTECHNICAL ENGINEERING PROPERTIES:

Foundations: Variable strength, especially in younger lavas due to ash beds, coriaceous or clinker layers, lava caves and other voids. Its aggregate can be used for concrete foundation.

Rock strength:Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa

UCS saturated MPa



Shear strength MPa

Friction angle

2.7 2 100-350

250 90 15 40 50

Hydrology: Young Lavas are generally good aquifers

Value: Good aggregate and valuable road stone

Name/type: Limestone, clastic sedimentary rock.

Sample properties:

Colour Various Hardness 3Streak White Cleavage None Lustre Vitreous Grain size Fine grains Fracture Uneven Tenacity Brittle Magnetism None Acid reaction Effervescence Feel Rough Specific gravity 2.3 – 2.7

Mineralogy: Limestone basically made up of calcite and aragonite, they also contain skeletal particles of some marine organisms such as coral, forams and mollusks.

Occurrence: “Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestone contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite and other minerals. It can also contain large nodules of chert, pyrite or siderite.” (King, Hobart. 2015).Structures: limestone is usually bedded in thick extensive successions, nodules of flint and marcasite are common.

Weathering: limestone breaks down when it come in contact with acids (mild or concentrated).

CIVIL/GEOTECHNICAL ENGINEERING PROPERTIES:

Foundations: limestone is good for foundation construction. Its aggregate can be used in the construction of base of roads.

Rock strength:

Density dry t/m3

Porosity %

Dry UCS range MPa

Dry UCS mean MPa

UCS saturated MPa



Shear strength MPa

Friction angle

2.2-2.6 5-20 50-120

71.8 30 3-27 5-25 10-50 35-45

Hydrology: Aquifer is efficient with diffuse and condult flow

Value: used as decorative and building stone.

References

Azomining.com. 'Pyrite - Occurrence, Properties, and Distribution'. N.p., 2015. Web. 7 Aug.

2015.

Azomining.com, 'Pyrite - Occurrence, Properties, and Distribution'. N.p., 2015. Web. 7 Aug. 2015.

Bragg, W. L., Brown, G. B.: Dic Struktur des Olivins. Z. Kristallogr. 63, 53R - 556 (1926)

King, Hobart. 'Marble: Metamorphic Rock: Pictures, Definition, And Properties’. Geology.com. N.p., 2015. Web. 8 Aug. 2015.

King, Hobart. 'Olivine: A Rock-Forming Mineral. Used as the Gemstone Peridot.’ Geology.com. N.p., 2015. Web. 7 Aug. 2015.

Kuebler, K.; Wang, A.; Haskin, L. A.; Jolliff, B. L. (2003). "A Study of Olivine Alteration to Iddingsite Using Raman Spectroscopy" (PDF). Lunar and Planetary Science 34: 1953.Minerals.net, 'Olivine: The Mineral Olivine, Peridot Information and Pictures'. N.p., 2015. Web. 7 Aug. 2015.

Mineralszone.com, 'Pyrite Uses, Pyrite Minerals, Pyrite Information, Pyrite Properties'. N.p., 2015. Web. 8 Aug. 2015.

Nature.berkeley.edu, 'Granite'. N.p., 2015. Web. 7 Aug. 2015.

Robinson-noble.com, 'Fractured Rock Aquifers'. N.p., 2015. Web. 5 Aug. 2015.

Ward-Harvey, ken. Fundamental Building Materials. 4th ed. universal publishers, 2009. Print.

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