Mineral Classification, Formation, and Global Deposits
Types of Minerals
Minerals are naturally occurring solid substances with a defined chemical composition and crystal structure. They are broadly categorized into several classes based on their chemical makeup:
Native Elements
Formed by atoms of a single element. These are mostly metals (e.g., iron, copper, silver, gold). Other non-metallic elements also occur natively (e.g., sulfur, graphite, diamond).
Sulfides
Formed by the combination of sulfur with one or more metals. They are important ores (sources of production) for various metals.
Halides
Compounds containing chlorine, bromine, iodine, or fluorine. Examples include common salt, which forms by water evaporation or from deposits of volcanic fumaroles.
Oxides
Compounds of various elements combined with oxygen. Some are of industrial interest, while others stand out as gems due to their colorful appearance.
Carbonates
Their composition involves the carbonate ion (CO3)2-. Some have important industrial applications.
Sulfates
Elements combined with the sulfate ion (SO4)2-. They encompass many mineral species, largely formed by metallic mineral alteration. They are also notable for their industrial applications.
Silicates
Incorporating silicon and oxygen, which are the most abundant elements in Earth’s crust. Examples include quartz, olivine, garnet, biotite, muscovite, orthoclase, tourmaline, and beryl.
Mineral Formation Processes
The formation of minerals is the result of a series of chemical and physical processes that have occurred throughout all geological ages and continue to manifest today.
Most minerals that occur in colorful crystals formed during the later stages of magma cooling.
Minerals originate through three main processes: igneous, sedimentary, and metamorphic.
Magmatic Processes
This process leads to the formation of minerals by the solidification of magma, which mainly consists of silica, metal oxides, gases, and vapors. Before reaching its current state, the Earth was formed by fluid magma, surrounded by a gas or vapor layer. This magma was composed of metallic elements mixed with oxygen and sulfur, forming oxides, sulfides, and silicates – the most important elements on Earth.
Upon cooling, minerals separated. First, poorly soluble and high-melting point minerals like iron and magnesium oxides and sulfides, and iron silicates with higher specific gravity, settled to the bottom, forming deep layers. Lighter silicates and other minerals rose, remaining in upper layers.
Contact or Thermal Metamorphism
Occurs around magmas, affecting the surrounding rocks. Temperature is the determining factor. The most characteristic minerals formed are garnet, cordierite, zoisite, tourmaline, pyroxene, and pyrite.
Regional Metamorphism
Develops over large areas of the Earth’s crust subject to subsidence, often at destructive plate boundaries. It is produced by the combined action of temperature and pressure.
Most characteristic minerals:
- 300°C: Talc, hematite, titanite, albite
- 400°C: Biotite, almandine, kyanite
- 600°C: Pyroxene, olivine, garnet, graphite, cordierite
Sedimentary Processes
Most minerals in sedimentary rocks originate from the mechanical erosion and chemical alteration of existing rocks.
When surface rocks are subjected to external geological agents (such as seas, rivers, wind, and temperature), their components (solid rock fragments, mineral ions dissolved in water, or remains of living organisms) become sediments. These sediments are then transported, processed, and deposited, forming sedimentary rocks through a set of physicochemical and biological processes known as diagenesis.
Mineral Resources of Venezuela
Venezuela has a wide variety of mineral deposits, distributed primarily within the Guayana Shield in southeastern Venezuela. This area contains important deposits of iron, bauxite, gold, diamonds, kaolin, barite, and manganese.
In the northern area of Venezuela, significant deposits of coal, nickel, zinc, copper, silver, lead, chromium, and silica sands are located. Mineral species such as titanium, platinum, lead, tungsten, dolomite, fluorite, mica, tin, cobalt, talc, graphite, marble, mercury, magnesite, vanadium, kyanite, bismuth, bentonite, asbestos, niobium, and rare earths are present and exploited, though their full potential as mining prospects remains unquantified.