Lecture 21
what does vermiculite produce?
a very high negative charge
What is shrink-swell phenomena?
affect many engineering properties of soils and clay liners.
T layers cannot bond together, so TOT sandwiches are separated by?
an interlayer space in which water or adsorbed cations may be present
Tetrahedron are?
central cation surrounded by 4 oxygens
Octahedron are?
central cation surrounded by 6 oxygens
Crystalline structure is determined by the?
chemical composition and arrangement of atoms in a given mineral
is vermiculite expandable or non-expandable?
expandable
what is the interlayer of chlorite?
extra octahedral
A tetrahedron is a?
geometric shape with four equal sides, or a "trigonal pyramid".
Finer particles have (greater/lesser) specific surface area?
greater
what is the surface area of vermiculite?
high
the chlorite group has what for its interlayer site?
hydroxide sheet
Diffractograms show?
interlayer spacing in clay minerals.
what does vermiculite have a lot of?
isomorphic substitution
What group doesn't have a interlayer site?
kaolinite
Different clay minerals are distinguished based on?
layering types, major cations, presence/absence of water in interlayer sites, and behavioral characteristics.
Different types of silicate minerals are produced by?
linking silicate tetrahedral in different, spatially repeating patterns.
what is the surface area of chlorite?
low
what is the surface area of illite?
low
Why is silicate mineral the most important?
makes up 90% of the earth's crust
What does non-expanding mean?
no water between layers
is chorite expandable or non-expandable?
non-expandable
Is illite expanding or non-expanding?
non-expanding
What group(s) has min swelling?
illite and chlorite
how thick is a T-O-T layer triplet?
10 angstroms
how thick is a TOTO sandwich?
14 angstroms
what is chlorite sometimes called?
2:2 TOTO
how thick is a T-O layer pair thickness? 7 angstroms
7 angstroms
Clay particle size is?
<0.06 mm
what soil has higher cation exchange capacity?
Clay-rich sediments and soils have higher CECs than clay-poor types
What is the charge of tetrahedron sheets?
Negative
What two ways can a isomorphous substitution leave a negative charge
Occupation of octahedral sites and addition of cations to interlayer sites
What is used to Identify clay minerals?
X-ray diffraction
what does isomorphous substitution leave?
a net negative charge.
Cation exchange capacity is influenced by?
clay-mineral type and specific surface area
is there swelling in chlorite?
no swelling
what is 1:1?
one tetrahedral sheet to one octahedral sheet (TO structure)
the Illite group has what for its interlayer site?
potassium ions
what is clay mineral behavior?
sheet like
What are clay minerals?
sheet silicates composed of layers of silicate tetrahedra
what is illite a product of?
silicate rock (e.g., feldspar) weathering
what layer is more expandable vermiculite or smectite?
smectite
What group(s) has max swelling?
smectite group
What can never exist by themselves?
tetrahedral
The cation exchange capacity describes?
the amount of exchangeable cations per unit soil mass
Specific surface area is?
the amount of surface per unit mass of material.
What is 2:1
two tetrahedral sheets to one octahedral sheet (TOT structure)
the smectite group has what for its interlayer site?
water molecules
the vermiculite group has what for its interlayer site?
water molecules
how does chlorite form?
weathering of Mg- and Fe-rich minerals