Natural materials are substances found in the natural environment that humans utilize for construction, clothing, tools, and countless other applications. These materials are extracted directly from the Earth, plants, or animals, forming a fundamental link between human civilization and the natural world. Unlike synthetic materials, which are engineered through chemical processes in a laboratory or factory, natural materials exist in their physical state without human intervention. The sources of these substances are broadly divided into two main categories: those derived from living organisms (biotic sources) and those sourced from geological formations (abiotic or mineral sources).
Defining the Scope of Natural Materials
The classification of a substance as a natural material relies on the degree of processing required before use. A true natural material must be found in a usable or near-usable form, requiring only minimal physical manipulation to be incorporated into a product. This minimal processing typically includes actions like cleaning, cutting, shaping, or simple mechanical separation, such as shearing wool or sawing a tree trunk into lumber.
This definition helps distinguish natural materials from the broader category of raw materials. For instance, crude oil is considered a raw material, but it is not a natural material because it requires extensive, energy-intensive chemical refining to be transformed into gasoline or plastics. Natural materials, by contrast, retain their original chemical and physical structure, ensuring that the finished product closely reflects its origin.
Materials Derived from Living Organisms
The biological world provides a vast array of materials, primarily from plants and animals, that possess unique structural properties. Plant-based materials offer varied utility, such as wood, which is composed of cellulose fibers and lignin, giving it strength for construction and furniture. Natural fibers are also derived from plants, including cotton, a nearly pure cellulose fiber that grows in a protective boll around the seeds of the plant.
Other plant products include natural rubber, which is harvested as latex, a milky fluid, primarily from the rubber tree through tapping the bark. This liquid polymer is then coagulated and dried for use. Animal-derived materials also offer unique fibers and structures. Wool is a protein fiber composed of keratin, sheared from sheep and other animals. Silk, another protein fiber, is produced by the larvae of the domesticated silkworm, which secretes the material to spin its cocoon. Finally, animal hides are converted into leather through tanning, a process that stabilizes the collagen protein structure to prevent decay and enhance durability.
Materials Sourced from Geological Processes
Materials sourced from the Earth’s crust are products of millions of years of geological activity, including volcanic action, sedimentation, and metamorphism. These inorganic substances are typically extracted through mining or quarrying and require only mechanical shaping for human use. Stone is a prime example, with materials like granite, marble, and slate being cut from the earth in blocks or slabs. Granite is an igneous rock with a crystalline structure, while marble is a metamorphic rock.
Sedimentary materials are also widely used, with sand and gravel being essential components found in riverbeds and ancient deposits. Clay is a fine-grained mineral material composed of hydrated aluminum silicates that becomes pliable when wet. It has been used for creating ceramics and bricks after being dug up and fired. Even metals can be considered natural materials when they are found in their elemental form, such as gold nuggets, or as easily reduced oxides, like certain iron ores.