HOW ARE MINERALS FORMED?
MINERALS They are inorganic solids of natural origin, with a characteristic chemical composition, having a regular atomic structure throughout. Industrial man-made diamonds are not considered true minerals but, that being said, there are also some organic minerals, such as amber, which purists are reluctant to call minerals, but meet at least three of the criteria for mineral composition and, therefore, the point is open for debate.
How many minerals are there? There are about 4,000 listed minerals on this planet, but only a few have gained popularity due to their pleasing appearance, often odd shapes, exquisite spectrum of colors, and commercial value. Minerals are generally made up of more than one element or compound. Those that are made up of a single element are called native elements e.g gold, silver, mercury, copper. Tea conquerors he fell in love with the gold of the New World and “liberated” it by ship cargo to fill the coffers of the Government and the Church in Spain. Silver also, along with Topaz, tourmaline, agate, ruby, diamond and many other precious rocks and minerals, have been highly prized since man was first enchanted by their beauty, commercial value, and status imparted to the wearer.
So how are minerals formed? Minerals can form in a wide variety of geological settings; inside volcanoes, at the bottom of deep oceans, deserts, salt lakes, and deep cooling reservoirs of molten rock. Furthermore, under the influence of heat or pressure, when solutions and gases containing concentrations of specific elements cool or evaporate, mineral growths are deposited within fissures or voids in rocks. These minerals are sometimes forced to pass as a suspension in water, the water then evaporates leaving the mineral deposits as crystals (for example, amethyst) when the rock void is not completely filled or as agates, when the rock is completely full. These minerals are only visible when the rock is broken open; It takes some skill to decide which rock to break! More on that later. An example of such crystal and mineral specimens for collectors are geodes which are round rocks that contain precipitated mineral salts, these being commonly Agates (caused by crystals of mineral salts that form within Basalt rocks), Amethysts, Quartz, Jasper.
Minerals don’t necessarily need heat or pressure to form; water saturated with mineral salts can leave deposits (stalactites) as it drips from the ceiling of a cave, forming corresponding stalagmites directly below, over the centuries, where the drops fall. Eventually, they both grow to meet and thicken over the years. Sometimes, as a novelty, tourists can hang an item on a rope in a cave, over which water saturated with calcium carbonate runs; over a period of a few months it is locked in a hardening tank of Calcium carbonate.
THE THREE TYPES OF ROCK.
Ok, the basic scene has been set, now let’s take a closer look at the different mechanisms involved in mineral formation. All minerals are made up of ROCKSwhich are an aggregate or mixture of various minerals and are the basic materials from which a mineral is formed.
The rocks can be:
Igneous – formed due to volcanic activity in the Earth’s core.
metamorphic – formed by pressure or heat (for example, colliding tectonic plates) on existing rocks, transforming them into another type of rock.
sedimentary – as a result of compaction in layers of rocky materials and/or shells.
Let’s examine these rocks a bit more:
IGNEOUS ROCKS(from Latin switched on – fire) can be further classified as Prayed extrusive.
mineral crystals formed from intruder Igneous rocks have a coarse structure because the cooling effect was slow and the crystals could grow for a long time, sometimes to a very large size, especially when molten rock (magma) is trapped underground and cools very slowly. Granite is an example of a commonly found intrusive rock. Other examples are:-
greenstone
gabbro
Pegmatite (Pegmatites are known to contain aquamarine, tourmaline, beryl, topaz, cassiterite, fluorite, apatite, tin, and tungsten plus a host of other minerals.
These rocks are generally only exposed after mountain-forming uplifts, when the rocks at the bottom are pushed to the surface due to the convergence of tectonic plates. The Himalayas, for example, are still being pushed up by convergent forces.
extrusive Rocks are magma ejected from volcanoes and cool rapidly on Earth’s surface. This means that their crystal structure is usually very small or microscopically small, since the crystals did not have enough time to develop. Obsidian (a black, glass-like rock that is still used by some surgeons because it keeps its sharp edge, down to a molecule!)
Andesite
Pumice
rhyolite
Human waste
METAMORPHIC ROCK MINERALS (from the Greek goal after, turn shape) are formed when enough heat and pressure change the original rock into an entirely new rock. The original rock can be sedimentary, igneous, or metamorphic. The most important metamorphic mechanism is heat, which changes the chemical structure of the rock at temperatures above 200 degrees Celsius, breaking down the crystalline structures of the rock and converting them into new minerals. If the temperature gets too high, the metamorphic action stops and the rocks become igneous. Marble it is a common example of metamorphosed limestone.
(hot water with dissolved ions) may also be responsible for changing parent rocks and is responsible for producing Sulfide minerals (for example Pyrite and Galena) and also Copper at the bottom of the sea when warm, mineral-enriched water comes into contact with seawater.
metamorphic minerals – most of the minerals in the following list are found exclusively in metamorphic rocks: –
Garnet
kyanite
chlorite
talcum powder
Graphite
tourmaline
Asbestos
Mica.
Board
serpentine
MINERALS OF SEDIMENTARY ROCKS. (from Latin sediment – a settlement). Sedimentary rocks are the building blocks from which almost all metamorphic rocks are formed; it is the sedimentary rocks that are dragged down or pushed up by tectonic activity. While igneous and metamorphic rocks produce some of the finest mineral/gemstone specimens, the minerals in sedimentary rocks are not as impressive in shape or range, although some sedimentary rocks may also include igneous and metamorphic minerals as they age. rocks crumble due to weathering and wear. dissolved in water. Sedimentary rocks are also a mirror of the past, the different layers tell a story of what the Earth’s climate was like during the millions of years that the rocks were formed, especially due to their fossil content since, unlike the other two Rock types, heat, and pressures produced in the formation of sedimentary rocks are not enough to destroy fossil evidence.
CLASSIFICATION OF SEDIMENTARY ROCKS.
CLASTIC Sedimentary rock is stratified or lithified (from the Greek stones – rock) by deposits of rubble eroded from other rocks (due to weathering, frost, glacial action or water). Most minerals in igneous rocks (with the exception of quartz, which is very hard) are attacked over time by water, acids, and alkalis, transforming into clay minerals and chemicals in solution. Other minerals in clastic sedimentary rock, such as zircon, rutile, and magnetite, are inert and highly resistant to mechanical and chemical breakdown.
Clastic rock also contains the minerals feldspar, quartz, amphiboles, and clays.
The minerals found in clastic sedimentary rocks belong to the classes of halides, sulfates, borates.
BIOGENIC SEDIMENTARY ROCKS They are made up of materials from living organisms, that is, corals, molluscs, and amoeboid organisms, which deposit layers of calcite on the ocean floors, which then form limestone. Other examples of minerals found in biogenic rocks are stromatolites and flint.
PRECIPITATED SEDIMENATRIAN ROCKS are formed when mineral solutions, for example seawater, evaporate and deposit minerals as Halite and gypsum.
And finally, a list of mineral classes (for the list lovers!)
mineral classes.
All minerals found in igneous, metamorphic, and sedimentary rocks can be classified as follows:
1. Elemental (Diamond, Gold, Silver)
2. Sulfides, Selenides, Tellurides, Arsenides, Antimonides, Bismuthides (Galena, Pyrite, Chalcoprite)
3. Halides (fluorspar, carnallite)
4. Oxides and Hydroxides (Corundum, Quartz, Hematite, Magnetite)
5. Sulfates, chromates, molybdates, tungstenates (barite, selenite)
6. Phosphates, arsenates, vanadates (variscite, mimetite, vanadinite)
7. Silicates (opal, zircon, talc, tourmalines, topaz)
8. Nitrates, Carbonates, Borates (Calcite, Malachite, Azurite)
9. Organic minerals (amber, whewellite, oxamite)
I hope the information has been helpful to you in your search for answers about how minerals are formed. The subject of Mineralogy can be developed in great scientific depth, but I have tried to present the information in a format that anyone can understand. I hope this little offer has whetted your appetite for further digging! Later I will add information on where and how to find some of the most popular minerals and gemstones. Happy hunting!