Definition

Loam is a soil type which mostly consist of sand and silt particles. A smaller amount of clay particles is present too. By weight, its mineral composition is about 40-40-20% concentration of sand-silt-clay respectively. If this proportions vary it is classified as the main type plus the name loam. For example: sandy loam, clay loam, etc. For a more accurate identification the graph on the right can be used.

Loamy dolomite

Dolomite is an organic sedimentary rock which is composed of small sea fossils. This rock type is less permeable than limestone due to the crystallization of the organic components. Moreover due to this aspect this rock type has a small increase in hardness and decrease in solubility in HCL. To distinguish this rock type from limestone chemical research is required. When loam has a fraction of organic sedimentary clasts it can be distinguished as loamy dolomite.

Loamy gravel

Gravel is a granular sedimentary rock. The grains need to have a diameter of more than 2 mm and less than 63 mm. De grains of this rock are coarser than those of sand and less coarse than those of pebbles and boulders. When gravel parts are present within a mixture of clay, silt and sand parts the soil type is defined as loamy gravel.

Loamy marl

Marl is a sedimentary rock consisting of clay, claystone and limestone. Marl is a transition phase from shale to limestone. The demarcation of this rock type is not very accurate, but in The Netherlands, one speaks of marl when 25%-75% of the rock is made up of chalk. Due to the platy and weakened structure this rock erodes very easily and is very vulnerable to weathering. When a marl is composed of clay, sand and silt particles and its fraction comes close to the one for loam it can be defined as loamy marl.

Loam soil triangle 

Loamy sand

This type of soil has between 0%-30% silt particles, between 70%-87% sand particles and between 10%-15% clay particles. The texture of this type of sand is something smoother than sand, but doesn't differ much.

Loamy silt

This type of soil has between 50%-80% silt particles, between 20%-50% sand particles and between 0%-37% clay particles. This is a relative wet soil type with some coarser grains present due to the sand fraction.

Silty loam

This type of soil has between 60%-72% silt particles, between 0%-20% sand particles and between 25%-40% clay particles.

Loamy/marl-like sandstone

Type of rock where the fraction sandstone is high, but also some organic components and silt/clay cement are present. If this sand consolidates with the clay and silt particles still present in its matrix the final result will be a loamy/marl-like sandstone.

References

• Kaufmann, Robert K.; Cutler J. Cleveland (2008). Environmental Science. McGraw-Hill. pp. 318–319. ISBN 978-0-07-298429-3.