Particle size (grain size) Information & Particle size (grain size) Links at HealthHaven.com

A display of sorted grains ranging in size from silt to very coarse sand.

Particle size or grain size refers to the diameter of a grain of granular material, such as sediment or the lithified particles in clastic rock. Granular material can range from very small colloidal particles, through clay, silt, sand, and gravel, to boulders.

In contrast, crystallite size is the size of a single crystal inside the grain. A single grain can be composed of several crystals.

[edit] Wentworth

The Wentworth scale or Udden-Wentworth scale is used in the United States. It names size ranges in inches.

[edit] Krumbein φ

A modification of the Wentworth scale created by W. C. Krumbein, the Krumbein phi scale, is a logarithmic scale defined by:

D = D 02 - φ

Such that:

D

is the diameter of the particle

D 0

is a reference diameter, equal to 1 mm

φ

is the phi scale

[edit] Chart

φ scale	size range	Wentworth range	name	other names
-8 to -∞	256-∞ mm	10.1-∞ in	boulder
-6 to -8	64–256 mm	2.5–10.1 in	cobble
-5 to -6	32–64 mm	1.26–2.5 in	very coarse gravel	pebble
-4 to -5	16–32 mm	0.63–1.26 in	coarse gravel	pebble
-3 to -4	8–16 mm	0.31–0.63 in	medium gravel	pebble
-2 to -3	4–8 mm	0.157–0.31 in	fine gravel	pebble
-1 to -2	2–4 mm	0.079–0.157 in	very fine gravel	granule
0 to -1	1–2 mm	0.039–0.079 in	very coarse sand
1 to 0	0.5–1 mm	0.020–0.039 in	coarse sand
2 to 1	0.25–0.5 mm	0.010–0.020 in	medium sand
3 to 2	125–250 µm	0.0049–0.010 in	fine sand
4 to 3	62.5–125 µm	0.0025–0.0049 in	very fine sand
8 to 4	3.9–62.5 µm	0.00015–0.0025 in	silt	mud
∞ to 8	1/∞-3.9 µm	1/∞ –0.00015 in	clay	mud
∞ to 10	1/∞-1 µm	1/∞–0.000039 in	colloid	mud

In some schemes^[which?] gravel is anything larger than sand and includes granule, pebble, cobble, and boulder in the above table. In the chart above, pebble covers the size range 4 to 64 mm.

[edit] See also

Wikimedia Commons has media related to: Sediments by particle size

Unified Soil Classification System
Soil texture
Photoanalysis
Optical granulometry
Sandpaper uses an older system of grit size.

[edit] References

W C Krumbein & L L Sloss, Stratigraphy and Sedimentation, 2nd edition (Freeman, San Francisco, 1963).
J A Udden, "Mechanical composition of clastic sediments", Bull. Geol. Soc. Am. 25:655–744 (1914).
C K Wentworth, "A scale of grade and class terms for clastic sediments", J. Geology 30:377–392 (1922).

Contents

[edit] Wentworth

[edit] Krumbein φ

[edit] Chart

[edit] See also

[edit] References