1.3 Mineral Formation and Occurrence
4 min read•july 31, 2024
Minerals form through various processes, from magma to biological activity. Understanding these formation mechanisms helps us grasp how Earth's diverse mineral assemblages came to be. This knowledge is crucial for interpreting the planet's geological history and resource potential.
Mineral stability depends on environmental conditions like temperature and pressure. By studying how minerals form and change, we gain insights into Earth's dynamic processes. This understanding is fundamental to mineralogy and its applications in geology, materials science, and resource exploration.
Mineral formation processes
Crystallization and precipitation
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- Crystallization from magma or lava forms minerals as molten rock cools and solidifies
- Occurs in both extrusive (volcanic) and intrusive (plutonic) igneous environments
- Produces primary igneous minerals (, feldspars, micas)
- from aqueous solutions creates minerals when dissolved ions combine
- Happens in water-rich settings (oceans, lakes, groundwater)
- Forms evaporite minerals (, ) and some carbonates ()
- Evaporation of mineral-rich solutions yields evaporite minerals
- Common in arid climates or closed basins
- Produces layered deposits of salts (, )
Metamorphism and solid-state reactions
- alters existing minerals under high pressure and temperature
- Causes recrystallization or formation of new mineral phases
- Creates metamorphic minerals (, , )
- between minerals produce new phases
- Occurs during metamorphism or weathering processes
- Forms minerals like or from alteration of others
Biological and uncommon processes
- Biological processes contribute to mineral formation
- Organisms create (shells, bones)
- Accumulation of organic material leads to fossil fuels (coal, oil)
- forms minerals directly from vapor to solid state
- Observed in volcanic fumaroles
- Produces minerals like or
Mineral formation environments
Igneous and hydrothermal settings
- Igneous environments encompass plutonic and volcanic settings
- Plutonic: deep-seated crystallization (, )
- Volcanic: rapid cooling at surface (, )
- create unique mineral-forming conditions
- Hot springs deposit minerals like or
- Deep-sea vents form massive sulfide deposits
Sedimentary and surface environments
- Sedimentary environments include terrestrial and marine settings
- Terrestrial: fluvial, lacustrine, and
- Marine: shallow to deep ocean basins
- Weathering environments alter minerals at Earth's surface
- Chemical weathering produces clay minerals
- Physical weathering concentrates resistant minerals (placer deposits)
Metamorphic and deep Earth settings
- Metamorphic environments range from local to regional scales
- Contact metamorphism near igneous intrusions forms skarns
- Regional metamorphism in orogenic belts creates and
- Mantle environments form deep-Earth minerals
- High-pressure conditions produce and other ultra-high pressure minerals
- Subduction zones generate hydrous minerals in the mantle wedge
Ore-forming environments
- concentrate metals through magmatic-hydrothermal processes
- Form large copper, molybdenum, and gold deposits
- form in submarine volcanic settings
- Produce zinc, copper, lead, and precious metal ores
Mineral stability and Earth's conditions
Thermodynamic principles and phase diagrams
- Mineral stability governed by
- Gibbs free energy determines stable mineral assemblages
- Enthalpy and entropy control reactions between minerals
- illustrate mineral stability fields
- Show stable phases across pressure-temperature ranges
- Useful for understanding metamorphic facies (greenschist, amphibolite)
Polymorphism and solid solutions
- occurs when minerals exist in multiple crystal structures
- Carbon system: graphite (low P-T) vs. diamond (high P-T)
- Silica polymorphs: quartz, tridymite, cristobalite
- series represent compositional variations
- Plagioclase feldspars (albite to anorthite)
- Olivine (forsterite to fayalite)
Kinetics and alteration processes
- Reaction determine mineral formation and transformation rates
- Affects preservation of metastable phases
- Influences texture development in rocks
- Weathering and alteration demonstrate mineral instability
- weathering to clay minerals
- Serpentinization of ultramafic rocks
- Retrograde metamorphism shows instability during uplift
- Chloritization of garnet
- Saussuritization of plagioclase
Mineral associations and genesis
Paragenesis and index minerals
- Mineral reveals formation sequences
- Crosscutting relationships in veins
- Reaction rims around minerals
- indicate specific metamorphic conditions
- Chlorite (low grade) to sillimanite (high grade)
- Useful for determining metamorphic facies
Ore and accessory mineral associations
- indicate deposit types
- Chalcopyrite + bornite + chalcocite (porphyry copper)
- Sphalerite + galena + pyrite (Mississippi Valley-type)
- in igneous rocks provide petrogenetic information
- Zircon for radiometric dating and provenance studies
- Apatite for magma volatile content
Textural and zoning patterns
- Mineral replacement textures offer evidence of changing conditions
- Pseudomorphs preserve original crystal shapes
- Corona textures in metamorphic rocks
- indicate evolving formation environments
- Oscillatory zoning in plagioclase (magma mixing)
- Prograde zoning in garnets (increasing metamorphic grade)
Key Terms to Review (53)
Accessory Minerals: Accessory minerals are secondary minerals that occur in small quantities within a rock, usually having no significant impact on the rock's overall classification. These minerals can provide valuable insights into the conditions of formation and the geological history of the host rock, often serving as indicators of specific environmental conditions during crystallization.
Alteration Processes: Alteration processes refer to the various physical and chemical changes that minerals undergo due to environmental factors, including weathering, hydration, and oxidation. These processes can significantly modify the original mineral composition and structure, impacting their stability and occurrence in nature. Understanding alteration processes is essential in the study of mineral formation as they provide insights into how minerals interact with their surroundings over time, influencing both their formation and availability in geological settings.
Basalt: Basalt is a dark, fine-grained volcanic rock that forms from the rapid cooling of low-viscosity lava rich in iron and magnesium. It is one of the most abundant types of igneous rock found on Earth and plays a crucial role in understanding the formation and classification of various Earth materials, particularly in relation to oceanic crust and volcanic activity.
Biogenic minerals: Biogenic minerals are minerals that are formed through biological processes, typically involving living organisms. These minerals can form in a variety of environments and play crucial roles in ecosystems, including the regulation of biogeochemical cycles and providing structure and support for various organisms.
Borax: Borax, also known as sodium borate, is a naturally occurring mineral and a key component of the borate mineral group. This compound is crucial in various industries and applications, especially in ceramics, glassmaking, and as a cleaning agent. Understanding its classification as an earth material and its formation processes enhances insights into its occurrences in nature and its importance in the context of other important sulfate and phosphate minerals.
Calcite: Calcite is a common and widely distributed mineral composed primarily of calcium carbonate (CaCO₃). Its significance stems from its role as a major component in sedimentary rocks, its various forms, and its importance in geological processes and industrial applications.
Chlorite: Chlorite is a group of phyllosilicate minerals characterized by their green color and layered structure, often formed in low to medium-grade metamorphic environments. These minerals are typically found in metamorphic rocks, where they can indicate specific conditions of formation and serve as important indicators of geological processes.
Crystallization: Crystallization is the process by which a solid forms from a liquid or gas, where the molecules or atoms arrange themselves in an ordered structure, creating a crystal. This process is fundamental in the formation of minerals and affects their characteristics, stability, and classification. Understanding how crystallization occurs provides insights into mineral stability, the arrangement of silicate structures, and the uniqueness of gemstones.
Diamonds: Diamonds are a crystalline form of carbon, renowned for their extraordinary hardness and brilliance, formed under high-pressure and high-temperature conditions deep within the Earth's mantle. Their formation typically occurs over millions of years, where carbon sources are subjected to extreme conditions, leading to the unique structure that gives diamonds their characteristic properties. Understanding diamonds involves exploring their geological origins, mineral associations, and occurrences in volcanic pipes and alluvial deposits.
Eolian Deposits: Eolian deposits are sedimentary formations that are created by the wind's action, consisting mainly of sand-sized particles that have been transported and accumulated in various environments. These deposits reflect the dynamic processes of erosion, transportation, and deposition driven by wind, often found in arid and semi-arid regions where vegetation is sparse. They play a crucial role in shaping landscapes and influencing mineral formation and occurrence, particularly in sandy terrains such as deserts and coastal areas.
Epidote: Epidote is a green to yellow-green mineral that typically occurs in metamorphic rocks and is known for its distinct crystal structure and composition. This mineral plays a key role in the classification of earth materials, particularly as a member of the silicate group due to its complex silicate structure, which contributes to its unique properties and formation processes.
Feldspar: Feldspar is a group of rock-forming minerals that are the most abundant in the Earth's crust, primarily composed of aluminum silicate combined with varying amounts of potassium, sodium, and calcium. This mineral group plays a vital role in the classification of earth materials, contributing to the formation and occurrence of many igneous, metamorphic, and sedimentary rocks.
Fluvial Deposits: Fluvial deposits are sediments that are transported and deposited by rivers and streams. These deposits often include a variety of materials such as sand, silt, clay, and gravel, which can accumulate in riverbeds, floodplains, and deltas. Understanding fluvial deposits is crucial because they provide insights into sedimentary processes and the environmental conditions during mineral formation and occurrence.
Gabbro: Gabbro is a coarse-grained, intrusive igneous rock primarily composed of plagioclase feldspar and pyroxene minerals. It forms when magma cools slowly beneath the Earth's surface, allowing large crystals to develop, and serves as a key example in understanding the classification of igneous rocks and their formation processes. Gabbro is often found in oceanic crust and can provide insights into the mineral composition and tectonic activity associated with its formation.
Garnet: Garnet is a group of silicate minerals that share similar crystal structures and chemical compositions, typically forming in metamorphic and igneous rocks. Known for their beautiful colors and high hardness, garnets are important in various geological processes and have significant industrial and gemstone applications.
Gneisses: Gneisses are a type of high-grade metamorphic rock characterized by their distinct banded or foliated appearance due to the segregation of mineral grains. Formed from the alteration of pre-existing rocks like granite or sedimentary rocks under high temperature and pressure conditions, gneisses contain a variety of minerals including quartz, feldspar, and mica. Their formation process is a key example of how minerals can change and evolve based on environmental factors.
Granite: Granite is a coarse-grained igneous rock primarily composed of quartz, feldspar, and mica, formed from the slow crystallization of magma beneath the Earth's surface. This rock type plays a significant role in understanding the classification of earth materials due to its mineral composition and formation processes. Its durability and aesthetic appeal also contribute to its extensive use in construction and as a decorative stone.
Gypsum: Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO₄·2H₂O. This mineral is significant due to its wide range of applications in construction, agriculture, and various industrial processes, as well as its presence in geological formations and sedimentary environments.
Halite: Halite is a naturally occurring mineral form of sodium chloride (NaCl), commonly known as rock salt. It is essential in the classification of Earth materials due to its distinctive properties and is formed through the evaporation of saline water, connecting it to various mineral formation processes and occurrences. Halite plays a significant role in the halide mineral category and is associated with sedimentary environments, highlighting its importance in the study of sedimentary minerals and their diagenesis.
Hydrothermal Systems: Hydrothermal systems refer to geological environments where heated water, often rich in minerals and gases, circulates through rocks and sediments. These systems play a crucial role in the formation of various mineral deposits and can significantly influence the occurrence of certain minerals, particularly those that are formed through processes like crystallization from solution.
Igneous Environment: An igneous environment refers to the geological settings where igneous rocks are formed through the cooling and solidification of molten magma or lava. These environments can be categorized into intrusive, where magma cools slowly beneath the Earth's surface, and extrusive, where lava cools quickly on the surface. Understanding these environments is crucial for studying mineral formation and occurrence, as they dictate the types of minerals that crystallize and the textures of the resulting rocks.
Index Minerals: Index minerals are specific minerals that are particularly useful for determining the conditions of formation and metamorphic history of rocks. These minerals are stable only within certain temperature and pressure ranges, making them key indicators for understanding the geological environment and processes that formed a rock. Their presence can provide insights into the metamorphic conditions and help construct a picture of the geological history of an area.
Kinetics: Kinetics is the branch of science that studies the rates of chemical reactions and the factors that influence those rates. In the context of mineral formation, kinetics helps to explain how quickly minerals can form or dissolve based on environmental conditions, temperature, and pressure. Understanding kinetics is essential for grasping how minerals develop in natural settings and how their stability can change over time.
Kyanite: Kyanite is a metamorphic mineral characterized by its distinct blue color and layered crystal structure, commonly formed under high-pressure and temperature conditions. This mineral is significant in understanding the processes of metamorphism, as it often occurs in schist and gneiss, revealing the dynamic environments in which it forms.
Lacustrine Deposits: Lacustrine deposits are sedimentary materials that accumulate in and around lakes, formed from the settling of particles in still or slow-moving water. These deposits can consist of various materials such as clay, silt, sand, and organic matter, often reflecting the environmental conditions of the lake at the time of deposition. Understanding lacustrine deposits is essential for comprehending how minerals and rocks are formed and distributed in different geological settings.
Metamorphic Environment: A metamorphic environment refers to the specific conditions under which metamorphic rocks form, including temperature, pressure, and the presence of chemically active fluids. These environments play a crucial role in determining the mineral composition and texture of the resulting metamorphic rocks, influencing their physical and chemical properties. Understanding these environments helps to identify the geological processes that lead to the transformation of pre-existing rocks into new forms.
Metamorphism: Metamorphism is the process by which existing rocks are transformed into new types of rocks through changes in temperature, pressure, and chemically active fluids. This transformation is crucial for understanding the formation and stability of various minerals, and it plays a significant role in the rock cycle by influencing mineral composition and texture.
Mica: Mica is a group of silicate minerals characterized by their layered structure, excellent cleavage, and shiny appearance. These minerals are essential in various geological processes and play a significant role in the formation of both igneous and metamorphic rocks, while also having important industrial applications due to their unique properties.
Obsidian: Obsidian is a naturally occurring volcanic glass formed when lava cools rapidly without crystallizing. This unique material is characterized by its glassy texture, sharp edges, and varied colors, which arise from the mineral content within the lava. Obsidian's formation process connects it to volcanic activity and the conditions under which it solidifies, making it significant in understanding earth materials and their classifications.
Ore Mineral Associations: Ore mineral associations refer to the specific groupings of mineral species that occur together in a geological setting, often indicative of the presence of economically valuable materials. These associations can provide important insights into the processes of mineral formation and the conditions under which they occurred, making them vital for identifying and exploiting mineral resources.
Ore-forming environment: An ore-forming environment refers to specific geological settings where mineral deposits accumulate, leading to the formation of economically valuable ores. These environments are crucial in determining the types of minerals that can form, their concentrations, and their accessibility for extraction. Understanding these settings helps in exploring and mining activities, as well as predicting where new deposits might be found.
Paragenesis: Paragenesis refers to the sequential formation of minerals in a geological setting, reflecting the conditions under which they were created and their relationships to each other. It provides insights into the history of mineral formation, including the environmental factors that influenced their development and how they coexist or replace one another. Understanding paragenesis helps to reconstruct geological processes and interpret the timing of mineral crystallization in various settings.
Phase Diagrams: Phase diagrams are graphical representations that show the stability of different phases of a substance under varying conditions of temperature and pressure. They provide crucial insights into the relationships between phases, such as solid, liquid, and gas, and help in understanding how minerals form and exist in various environments.
Polymorphism: Polymorphism refers to the ability of a mineral to exist in more than one crystal structure or form while having the same chemical composition. This phenomenon is important because it illustrates how different environmental conditions, such as temperature and pressure, can influence the arrangement of atoms in a mineral. Polymorphic minerals can exhibit significantly different physical properties, which can impact their formation, occurrence, and classification.
Porphyry Deposits: Porphyry deposits are large, low-grade ore bodies that contain significant amounts of copper, gold, and other metals, typically formed from hydrothermal processes associated with igneous intrusions. These deposits are characterized by their disseminated mineralization, often found within a stockwork of veins in a granitic or volcanic rock environment. The connection between porphyry deposits and mineral formation highlights how specific geological settings and processes can lead to the accumulation of economically important minerals.
Potash: Potash refers to a variety of potassium-containing minerals and compounds, primarily used as a fertilizer to enhance plant growth. Its significance lies in its ability to supply essential nutrients to crops, improving agricultural productivity while also playing a role in mineral formation and occurrence through processes like evaporation in saline water bodies.
Precipitation: Precipitation is the process by which dissolved substances in a solution form solid particles as they become supersaturated. This phenomenon plays a crucial role in mineral formation and transformation, influencing the development of various mineral types and their occurrences in nature.
Quartz: Quartz is a common and abundant mineral composed of silicon dioxide (SiO₂) that forms in a variety of geological environments. Known for its hardness and resistance to weathering, quartz plays a significant role in the classification of minerals and is essential for understanding various geological processes.
Salammoniac: Salammoniac is a mineral composed primarily of ammonium chloride (NH4Cl), often found in volcanic environments and as a sublimation product in certain chemical reactions. This mineral plays a significant role in the formation of other minerals and can occur in various geological settings, often associated with the oxidation of ammonium-rich minerals or the evaporation of saline waters.
Schists: Schists are a type of metamorphic rock characterized by their well-developed foliation and a significant presence of platy minerals such as mica. They form under moderate to high-grade metamorphic conditions, where the original rock undergoes physical and chemical changes due to heat, pressure, and the presence of chemically active fluids. This transformation results in a layered appearance, often with visible crystals that can be observed with the naked eye, linking schists to the processes of mineral formation and occurrence in various geological settings.
Sedimentary environment: A sedimentary environment refers to the specific conditions and processes under which sediments are deposited and accumulated, shaping the characteristics of sedimentary rocks. These environments include factors like water depth, energy levels, and the presence of organisms, which all influence the type and distribution of sediments. Understanding sedimentary environments is crucial for interpreting geological history and the formation of mineral deposits within sedimentary rocks.
Sinter: Sinter is a term that describes a type of sedimentary rock formed from the precipitation of minerals, particularly in geothermal areas. It often consists of silica and is created through processes like evaporation and deposition from hot springs or geysers. Sinter can play a key role in mineral formation by trapping other minerals and affecting the local geological environment.
Solid Solution: A solid solution is a homogeneous mixture of two or more minerals or elements where the atoms can substitute for one another in the crystal lattice without changing the overall structure. This concept highlights how minerals can vary in composition while maintaining their essential properties, which is crucial for understanding mineral formation, structural diversity, and classification in various mineral types.
Solid-state reactions: Solid-state reactions are chemical processes that occur between solid materials, leading to the formation of new phases or compounds without any change in the solid state. These reactions play a critical role in mineral formation, often occurring under conditions of high temperature and pressure, allowing minerals to develop through atomic rearrangement rather than melting. This concept is essential for understanding how minerals evolve and interact within the Earth's crust.
Staurolite: Staurolite is a brown to black mineral that is primarily composed of iron, aluminum, and silicate, and is known for its characteristic cross-shaped crystals. This mineral typically forms under high-grade metamorphic conditions and is often found in schist and gneiss, making it significant in understanding metamorphic processes and rock formation.
Sublimation: Sublimation is the process by which a solid transitions directly into a gas without first becoming a liquid. This physical change is important in mineral formation, as it influences the way minerals are deposited and how they interact with their environment. Understanding sublimation helps explain certain geological processes, such as the formation of specific mineral deposits that occur under particular temperature and pressure conditions.
Sulfur: Sulfur is a non-metallic element represented by the symbol 'S' and atomic number 16, playing a crucial role in various geological and biological processes. It is commonly found in minerals and forms compounds with other elements, significantly contributing to mineral formation and occurrence. Sulfur is known for its distinct yellow color in its native form and its ability to form different crystal habits and forms, which can be observed in various mineral deposits.
Textural Patterns: Textural patterns refer to the arrangement and organization of mineral grains within a rock, which can reveal important information about the conditions of mineral formation and occurrence. These patterns can help identify the processes that created the rock, such as cooling rates, pressure, and chemical environments, giving insights into its geological history. Understanding textural patterns is essential for interpreting the formation environment of minerals and rocks.
Thermodynamic Principles: Thermodynamic principles refer to the fundamental concepts governing the relationships between heat, work, temperature, and energy within a system. In the context of mineral formation and occurrence, these principles help explain how minerals crystallize from molten rock or precipitate from solutions, as well as how temperature and pressure influence their stability and transformations in various geological environments.
Travertine: Travertine is a type of limestone that forms through the precipitation of calcium carbonate from mineral springs, especially hot springs. It typically appears in a banded, layered structure and is characterized by its porous texture, making it a popular choice for architectural and decorative purposes. This unique mineral formation process highlights the interaction between geological and hydrological systems.
Volcanogenic massive sulfide deposits: Volcanogenic massive sulfide deposits are mineral accumulations formed from hydrothermal fluids that are released during volcanic activity, often found at mid-ocean ridges and volcanic arcs. These deposits primarily consist of sulfide minerals, such as pyrite and chalcopyrite, and can contain valuable metals like copper, lead, zinc, and gold. Their formation is closely linked to the interaction of seawater with magma, creating a unique environment for mineralization.
Weathering Environment: A weathering environment refers to the specific conditions under which weathering processes occur, leading to the breakdown and alteration of rocks and minerals. This environment is influenced by factors such as climate, topography, vegetation, and time, all of which play significant roles in the type and rate of weathering that takes place. Understanding the weathering environment is crucial for comprehending how minerals form and occur in different geological settings.
Zoning Patterns: Zoning patterns refer to the distinct compositional variations observed within a mineral, typically as a result of changes in environmental conditions during its formation. These variations can manifest as differences in color, mineral content, or crystal size, and they often reflect the conditions present during the mineral's crystallization. Understanding zoning patterns is crucial for interpreting the formation history and environmental conditions of minerals.