Chapter 2
Primary Minerals
Abstract This chapter introduces the primary minerals that are relatively common
in soils. It first presents the accepted views on the elemental compositions of the
Earth’s crust, rocks, and minerals. Soils at the top of the Earth’s crust are also within
the rock cycle. Silicate and silica minerals, which constitute more than 90% of the
minerals in the Earth’ crust, are outlined. Samples of relatively un-weathered and
weathered primary minerals were obtained from new volcanic ash and soils derived
from granitic rocks, respectively. Quartz is highly resistant to weathering, whereas
biotite in soil is altered in moist climates. The composition of primary minerals in
soils is affected by the types of parent rocks, weathering, sorting, and other soilforming factors, resulting in mineral compositions that deviate from the average
mineral composition of the Earth’s crust.
2.1 Introduction
Ranging from clay to rock fragment, soil particles have a wide size distribution.
Minerals in soils are divided conceptually into primary and secondary minerals.
According to the Glossary of Soil Science Terms (Glossary of soil science terms
committee 2008), a primary mineral is a mineral that has not been altered chemically
since its crystallization from molten lava and deposition. A mineral is defined as an
inorganically formed, naturally occurring homogeneous solid with a definite chemical composition and an ordered atomic arrangement. These definitions are followed
in this monograph.
Soils form by widely different processes, and their states range from
un-weathered to highly weathered. They thus show various compositions of primary
and secondary materials. The particle-size fraction of most primary minerals is
the larger than 2 μm fraction, which includes silt, sand, and gravel. Primary minerals
can be separated from soil by the particle-size fractionation method described in the
Sect. 1.4.
The major primary minerals in soil are silicate and silica minerals. Other minerals
include titanomagnetite, other iron minerals, and apatite. The sand fraction of soils
© The Author(s) 2018
M. Nanzyo, H. Kanno, Inorganic Constituents in Soil,
https://doi.org/10.1007/978-981-13-1214-4_2
11
Primary Minerals
Abstract This chapter introduces the primary minerals that are relatively common
in soils. It first presents the accepted views on the elemental compositions of the
Earth’s crust, rocks, and minerals. Soils at the top of the Earth’s crust are also within
the rock cycle. Silicate and silica minerals, which constitute more than 90% of the
minerals in the Earth’ crust, are outlined. Samples of relatively un-weathered and
weathered primary minerals were obtained from new volcanic ash and soils derived
from granitic rocks, respectively. Quartz is highly resistant to weathering, whereas
biotite in soil is altered in moist climates. The composition of primary minerals in
soils is affected by the types of parent rocks, weathering, sorting, and other soilforming factors, resulting in mineral compositions that deviate from the average
mineral composition of the Earth’s crust.
2.1 Introduction
Ranging from clay to rock fragment, soil particles have a wide size distribution.
Minerals in soils are divided conceptually into primary and secondary minerals.
According to the Glossary of Soil Science Terms (Glossary of soil science terms
committee 2008), a primary mineral is a mineral that has not been altered chemically
since its crystallization from molten lava and deposition. A mineral is defined as an
inorganically formed, naturally occurring homogeneous solid with a definite chemical composition and an ordered atomic arrangement. These definitions are followed
in this monograph.
Soils form by widely different processes, and their states range from
un-weathered to highly weathered. They thus show various compositions of primary
and secondary materials. The particle-size fraction of most primary minerals is
the larger than 2 μm fraction, which includes silt, sand, and gravel. Primary minerals
can be separated from soil by the particle-size fractionation method described in the
Sect. 1.4.
The major primary minerals in soil are silicate and silica minerals. Other minerals
include titanomagnetite, other iron minerals, and apatite. The sand fraction of soils
© The Author(s) 2018
M. Nanzyo, H. Kanno, Inorganic Constituents in Soil,
https://doi.org/10.1007/978-981-13-1214-4_2
11