Lecture 3 Core Soil Properties: Soil Mineralogy

A set of vocabulary-style flashcards covering key concepts from the lecture notes on soil mineralogy, primary vs secondary minerals, and related properties.

Primary minerals

Minerals that persist with little change in composition and are typically found in the sand and silt fractions of soil.

Secondary minerals

Minerals formed by breakdown and biogeochemical weathering of less resistant minerals; found in clay and fine silt fractions (examples: phyllosilicate clays and iron oxides).

Quartz

A primary mineral; highly resistant to weathering and commonly found in sand and silt fractions.

Kaolinite

A clay mineral (phyllosilicate) with a layered structure; an example of a secondary mineral.

Smectite

A clay mineral (phyllosilicate) known for expandable layers and high negative charge.

Phyllosilicate clays

A group of clay minerals with sheet silicate structures (includes kaolinite and smectite).

Iron oxides

Secondary minerals formed by weathering or precipitation; give soils a red color when oxidized and grey-blue when reduced.

Calcium carbonate

Mineral found in limestone; gives white-grey soil color; more concentrated deeper in the soil profile (common in Prairie soils).

Negative charge of clay minerals

Attracts positively charged molecules and ions, contributing to water and nutrient retention.

Cation exchange capacity (CEC)

Soil's ability to hold and exchange positively charged ions (cations) due to negative charges on clays and organic matter.

Mechanical weathering

Physical breakdown of rocks and minerals into smaller pieces without chemical change.

Biogeochemical weathering

Chemical alteration of minerals driven by biological and geochemical processes.

Specific surface area

High surface area of clay minerals, which enhances water retention, nutrient exchange, and microorganism habitats.

Pore space

The void space in soil that can contain water and air.

Soil texture

Relative proportions of sand, silt, and clay in soil.

Soil mineralogy

The study of minerals in soils and their properties, including primary and secondary minerals.

Soil organic matter

The organic component of soil, commonly about 5% in ideal conditions.

Saline soils

Soils with high sodium salts, often in areas with marine shale; can limit crop productivity.

Red color of soil is an indication of:

oxidized iron

Grey-blue color of soil indicates:

reduced iron under wet conditions

Canadian soils origin

Inherited minerals from bedrock, transported by glaciers and meltwaters; developed on Late Wisconsin glacial sediments; soils are relatively young (5,000–18,000 years).

Calcium carbonate color indicator

White colour in soils due to calcium carbonate; higher concentrations deeper in the profile.

Ideal soil composition

About 45% minerals, 5% soil organic matter, and 50% pore space.

Particle size order

Sand > Silt > Clay in terms of particle size.

Clay minerals and charge

Clay minerals are negatively charged, which drives the exchange and retention of positively charged nutrients (cations).