1.
Nepheline
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Nepheline crystals are rare and belong to the hexagonal system, usually having the form of a short, six-sided prism terminated by the basal plane. It is found in compact, granular aggregates, and can be white, yellow, gray, green, the hardness is 5.5 -6, and the specific gravity 2.56 -2.66. It is often translucent with a greasy luster, an important determinative character of nepheline is the ease with which it is decomposed by hydrochloric acid, with separation of gelatinous silica and cubes of salt. For this reason, a crystal of nepheline becomes cloudy when immersed in acid. It has therefore been suggested that the formula, AlSiO4. The mineral is one liable to alteration, and in the laboratory various substitution products of nepheline have been prepared. In nature it is altered to zeolites, sodalite, kaolin. Two varieties of nepheline are distinguished, differing in their appearance and in their mode of occurrence, being analogous in these respects to sanidine. Glassy nepheline has the form of small, colorless, transparent crystals and it is characteristic of the later volcanic rocks rich in alkalis, such as phonolite, nepheline-basalt, leucite basalt, etc. and also of certain dike-rocks, such as tinguaite. The best crystals occur with mica, sanidine, garnet, etc. in the cavities of the ejected blocks of Monte Somma. It forms a constituent of certain alkaline plutonic rocks of the nepheline syenite series. The color and greasy luster of elaeolite are due to the presence of numerous microscopic enclosures of other minerals and this article incorporates text from a publication now in the public domain, Leonard James Spencer. Media related to Nepheline at Wikimedia Commons
2.
Sweden
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Sweden, officially the Kingdom of Sweden, is a Scandinavian country in Northern Europe. It borders Norway to the west and Finland to the east, at 450,295 square kilometres, Sweden is the third-largest country in the European Union by area, with a total population of 10.0 million. Sweden consequently has a low density of 22 inhabitants per square kilometre. Approximately 85% of the lives in urban areas. Germanic peoples have inhabited Sweden since prehistoric times, emerging into history as the Geats/Götar and Swedes/Svear, Southern Sweden is predominantly agricultural, while the north is heavily forested. Sweden is part of the area of Fennoscandia. The climate is in very mild for its northerly latitude due to significant maritime influence. Today, Sweden is a monarchy and parliamentary democracy, with a monarch as head of state. The capital city is Stockholm, which is also the most populous city in the country, legislative power is vested in the 349-member unicameral Riksdag. Executive power is exercised by the government chaired by the prime minister, Sweden is a unitary state, currently divided into 21 counties and 290 municipalities. Sweden emerged as an independent and unified country during the Middle Ages, in the 17th century, it expanded its territories to form the Swedish Empire, which became one of the great powers of Europe until the early 18th century. Swedish territories outside the Scandinavian Peninsula were gradually lost during the 18th and 19th centuries, the last war in which Sweden was directly involved was in 1814, when Norway was militarily forced into personal union. Since then, Sweden has been at peace, maintaining a policy of neutrality in foreign affairs. The union with Norway was peacefully dissolved in 1905, leading to Swedens current borders, though Sweden was formally neutral through both world wars, Sweden engaged in humanitarian efforts, such as taking in refugees from German-occupied Europe. After the end of the Cold War, Sweden joined the European Union on 1 January 1995 and it is also a member of the United Nations, the Nordic Council, Council of Europe, the World Trade Organization and the Organisation for Economic Co-operation and Development. Sweden maintains a Nordic social welfare system that provides health care. The modern name Sweden is derived through back-formation from Old English Swēoþēod and this word is derived from Sweon/Sweonas. The Swedish name Sverige literally means Realm of the Swedes, excluding the Geats in Götaland, the etymology of Swedes, and thus Sweden, is generally not agreed upon but may derive from Proto-Germanic Swihoniz meaning ones own, referring to ones own Germanic tribe
3.
Intrusive rock
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Intrusive rock is formed when magma crystallizes and solidifies underground to form intrusions, for example plutons, batholiths, dikes, sills, laccoliths, and volcanic necks. Intrusive rock forms within Earths crust from the crystallization of magma, magma slowly pushes up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the magma slowly cools into a solid, the different parts of the magma crystallize into rocks, many mountain ranges, such as the Sierra Nevada in California, are formed mostly from large granite intrusions, see Sierra Nevada Batholith. Intrusions are one of the two ways igneous rock can form, the other is extrusive rock, that is, an eruption or similar event. Technically speaking, an intrusion is any formation of igneous rock, rock formed from magma that cools. In contrast, an extrusion consists of rock, rock formed above the surface of the crust. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons, plutonic rocks form 7% of the Earths current land surface. Coarse-grained intrusive igneous rocks form at depth within the earth are called abyssal while those that form near the surface are called subvolcanic or hypabyssal. The term intrusive suite seems near synonymous, there is, however, a modest difference, An intrusive suite is a group of plutons related in time and space. Intrusions vary widely, from mountain-range-sized batholiths to thin veinlike fracture fillings of aplite or pegmatite, when exposed by erosion, such batholiths may occupy large areas. A well-known example of an intrusion is Devils Tower, another is Shiprock, New Mexico, USA. Be the pluton is large, it may be called a batholith or a stock, Intrusive rocks are characterized by large crystal sizes, and as the individual crystals are visible, the rock is called phaneritic. This is as the magma cools underground, and while cooling may be fast or slow, cooling is slower than on the surface, if it runs parallel to rock layers, it is called a sill. If an intrusion makes rocks above rise to form a dome, as heat dissipation is slow, and as the rock is under pressure, crystals form, and no vitreous rapidly chilled matter is present. The intrusions did not flow while solidifying, hence do not show lines, contained gases could not escape through the thick strata, thus form cavities, which can often be observed. Because their crystals are of the rough equal size, these rocks are said to be equigranular, there is typically no distinction between a first generation of large well-shaped crystals and a fine-grained ground-mass. Earlier crystals originated at a time when most of the rock was still liquid and are more or less perfect, later crystals are less regular in shape because they were compelled to occupy the spaces left between the already-formed crystals. The former case is said to be idiomorphic, the latter is xenomorphic, there are also many other characteristics that serve to distinguish the members of these two groups
4.
Igneous rock
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Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava, the magma can be derived from partial melts of existing rocks in either a planets mantle or crust. Typically, the melting is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, Igneous and metamorphic rocks make up 90–95% of the top 16 km of the Earths crust by volume. Igneous rocks form about 15% of the Earths current land surface, most of the Earths oceanic crust is made of igneous rock. In terms of modes of occurrence, igneous rocks can be either intrusive or extrusive, the mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body, typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. When the magma solidifies within the earths crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, the central cores of major mountain ranges consist of intrusive igneous rocks, usually granite. When exposed by erosion, these cores may occupy huge areas of the Earths surface, intrusive igneous rocks that form at depth within the crust are termed plutonic rocks and are usually coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks, hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths. Extrusive igneous rocks, also known as rocks, are formed at the crusts surface as a result of the partial melting of rocks within the mantle. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks and they are formed by the cooling of molten magma on the earths surface. The magma, which is brought to the surface through fissures or volcanic eruptions, hence such rocks are smooth, crystalline and fine-grained. Basalt is an extrusive igneous rock and forms lava flows, lava sheets. Some kinds of basalt solidify to form long polygonal columns, the Giants Causeway in Antrim, Northern Ireland is an example. The molten rock, with or without suspended crystals and gas bubbles, is called magma and it rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava, eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of volcanic activity
5.
Granite
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Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be white, pink, or gray in color. The word granite comes from the Latin granum, a grain, in reference to the structure of such a holocrystalline rock. By definition, granite is a rock with at least 20% quartz. The term granitic means granite-like and is applied to granite and a group of igneous rocks with similar textures and slight variations in composition. Occasionally some individual crystals are larger than the groundmass, in case the texture is known as porphyritic. A granitic rock with a texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks, petrographic examination is required for identification of specific types of granitoids. The extrusive igneous rock equivalent of granite is rhyolite, Granite is nearly always massive, hard and tough, and therefore it has gained widespread use throughout human history, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 •1019 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C, it is reduced in the presence of water. Granite has poor primary permeability, but strong secondary permeability, true granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite, when a granitoid contains less than 10% orthoclase, it is called tonalite, pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-mica granite, two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. A worldwide average of the composition of granite, by weight percent, based on 2485 analyses. Much of it was intruded during the Precambrian age, it is the most abundant basement rock that underlies the relatively thin veneer of the continents. Outcrops of granite tend to form tors and rounded massifs, granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite often occurs as small, less than 100 km² stock masses
6.
Quartz
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Quartz is the second most abundant mineral in Earths continental crust, behind feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones, since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. The word quartz is derived from the German word Quarz and its Middle High German ancestor twarc, the Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning icy cold, because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end, well-formed crystals typically form in a bed that has unconstrained growth into a void, usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, a quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward. α-quartz crystallizes in the crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the system, space group P6222 and P6422. These space groups are truly chiral, both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is an identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties, the cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, carnelian or sard, onyx, heliotrope, amethyst is a form of quartz that ranges from a bright to dark or dull purple color. The worlds largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, sometimes amethyst and citrine are found growing in the same crystal. It is then referred to as ametrine, an amethyst is formed when there is iron in the area where it was formed
7.
Mafic
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Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, common mafic rocks include basalt, dolerite and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar, chemically, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, water and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less violent than felsic-lava eruptions. Most mafic-lava volcanoes are shield volcanoes, like those in Hawaii, QAPF diagram List of minerals List of rock types
8.
Felsic
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In geology, felsic refers to igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium. It refers to those rocks rich in minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium. They are usually light in color and have specific gravities less than 3, the most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars, in terms of chemistry, felsic minerals and rocks are at the other end of the elemental spectrum from the mafic minerals and rocks. In modern usage, the acid rock, although sometimes used as a synonym, refers to a high-silica-content volcanic rock. The term was used broadly in older geologic literature. It is considered archaic now, as the acidic and basic rock were based on an incorrect idea, dating from the 19th century. The term felsic combines the words feldspar and silica, in order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals, namely quartz, orthoclase and plagioclase. Rocks with greater than 90% felsic minerals can also be called leucocratic, the chemical name of a felsic rock is given according to the TAS classification of Le Maitre. However, this applies to volcanic rocks. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, there are examples known of highly sheared granites which can be mistaken for rhyolites. For phaneritic felsic rocks, the QAPF diagram should be used, the rock texture thus determines the basic name of a felsic rock. QAPF diagram List of minerals List of rock types Le Maitre, igneous Rocks, A Classification and Glossary of Terms 2nd edition, Cambridge
