Particle size (grain size)

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Particle size (grain size)

Particle size, also called grain size, refers to the diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle....
of individual grains of sediment

Sediment

Sediment is any particulate matter that can be sediment transport by fluid dynamics, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers....
, or the lithified

Lithification

Lithification is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithification is a process of porosity destruction through Compaction and cementation ....
particles in clastic rocks. The term may also be applied to other granular material

Granular material

A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact ....
s. This is different from the crystallite

Crystallite

A crystallite is a domain of solid-state matter that has the same structure as a single crystal. Metallurgy often refer to crystallites as "grains"....
size, which is the size of a single crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
inside the particles or grains. A single grain can be composed of several crystal

Crystal

Granular material

A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact ....
can range from very small colloidal particles

Colloid

A colloid is a type of chemical mixture where one substance is dispersed evenly throughout another. The particles of the dispersed substance are only suspended in the mixture, unlike a solution, where they are completely dissolved within....
, through clay

Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
, silt

Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
, sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
, and gravel

Gravel

Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....
, to boulder

Boulder

In geology, a boulder is a rock with Particle size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
s.

Size ranges define limits of classes that are given names in the Wentworth scale (or Udden-Wentworth) used in the United States

United States

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Encyclopedia

Particle size, also called grain size, refers to the diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle....
of individual grains of sediment

Sediment

Lithification

Granular material

A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact ....
s. This is different from the crystallite

Crystallite

Crystal

Granular material

Colloid

Clay

Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
, sand

Sand

Gravel

Boulder

United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
. The Krumbein phi
PHI

PHI is a three-letter acronym or abbreviation that can refer to:* Post-Polio Health International* Protected Health Information as part of the HIPAA regulations...
(φ) scale, a modification of the Wentworth scale created by W. C. Krumbein, (Krumbein & Sloss 1963) is a logarithmic scale

Logarithmic scale

A logarithmic scale is a scale that uses the logarithm of a physical quantity instead of the quantity itself.Presentation of data on a logarithmic scale can be helpful when the data covers a large range of values – the logarithm reduces this to a more manageable range....
computed by the equation where is the Krumbein phi scale, is the diameter

Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle....
of the particle, is a reference diameter, equal to 1 mm

Millimetre

The millimetre is a Units of measurement of length in the metric system, equal to one thousandth of a metre, which is the current International System of Units SI base unit of length....
to make the equation dimensionally consistent

Dimensional analysis

Dimensional analysis is a conceptual tool often applied in physics, chemistry, and engineering to understand physical situations involving certain physical quantities....
. This equation can be rearranged to find diameter using φ:

φ scale	Size range (metric)	Size range (inches)	Aggregate class (Wentworth)	Other names
< -8	> 256 mm	> 10.1 in	Boulder Boulder In geology, a boulder is a rock with Particle size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
-6 to -8	64–256 mm	2.5–10.1 in	Cobble Cobble Cobble may refer to:* A particular size of rock, larger than gravel* Cobblestone, partially-rounded rocks used for road paving* Hammerstone, a prehistoric stone tool...
-5 to -6	32–64 mm	1.26–2.5 in	Very coarse gravel Gravel Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....	Pebble Pebble A pebble is a clastic rocks of rock with a particle size of 4 to 64 millimeters based on the Krumbein phi scale of sedimentology. It is generally considered to be larger than gravel and smaller than cobble....
-4 to -5	16–32 mm	0.63–1.26 in	Coarse gravel Gravel Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....	Pebble Pebble A pebble is a clastic rocks of rock with a particle size of 4 to 64 millimeters based on the Krumbein phi scale of sedimentology. It is generally considered to be larger than gravel and smaller than cobble....
-3 to -4	8–16 mm	0.31–0.63 in	Medium gravel Gravel Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....	Pebble Pebble A pebble is a clastic rocks of rock with a particle size of 4 to 64 millimeters based on the Krumbein phi scale of sedimentology. It is generally considered to be larger than gravel and smaller than cobble....
-2 to -3	4–8 mm	0.157–0.31 in	Fine gravel Gravel Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....	Pebble Pebble A pebble is a clastic rocks of rock with a particle size of 4 to 64 millimeters based on the Krumbein phi scale of sedimentology. It is generally considered to be larger than gravel and smaller than cobble....
-1 to -2	2–4 mm	0.079–0.157 in	Very fine gravel Gravel Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....	Granule Granule Granule is a generic term used for a small particle or grain. The generic term is used in a variety of specific contexts.* Granule , visible structures in the photosphere of the Sun arising from activity in the Sun's convective zone...
0 to -1	1–2 mm	0.039–0.079 in	Very coarse sand Sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
1 to 0	0.5–1 mm	0.020–0.039 in	Coarse sand Sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
2 to 1	0.25–0.5 mm	0.010–0.020 in	Medium sand Sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
3 to 2	125–250 µm Micrometre A micrometre or micron is one Micro- of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron....	0.0049–0.010 in	Fine sand Sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
4 to 3	62.5–125 µm	0.0025–0.0049 in	Very fine sand Sand Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
8 to 4	3.9–62.5 µm	0.00015–0.0025 in	Silt Silt Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....	Mud MUD In Online game, a MUD , pronounced /m?d/, is a multi-user real-time virtual world described entirely in text. It combines elements of role-playing games, hack and slash, interactive fiction, and online chat....
> 8	< 3.9 µm	< 0.00015 in	Clay Clay Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....	Mud MUD In Online game, a MUD , pronounced /m?d/, is a multi-user real-time virtual world described entirely in text. It combines elements of role-playing games, hack and slash, interactive fiction, and online chat....
>10	< 1 µm	< 0.000039 in	Colloid Colloid A colloid is a type of chemical mixture where one substance is dispersed evenly throughout another. The particles of the dispersed substance are only suspended in the mixture, unlike a solution, where they are completely dissolved within....	Mud MUD In Online game, a MUD , pronounced /m?d/, is a multi-user real-time virtual world described entirely in text. It combines elements of role-playing games, hack and slash, interactive fiction, and online chat....

In some schemes "gravel" is anything larger than sand (>2.0 mm), and includes "granule", "pebble", "cobble", and "boulder" in the above table. In this scheme, "pebble" covers the size range 4 to 64 mm (-2 to -6 φ).

Particle size (grain size)

See also