|
Spherulite 1
In petrology, spherulites () are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone, and rhyolite as globules about the size of millet seed or rice grain, with a duller luster than the surrounding glassy base of the rock, and when they are examined with a lens they prove to have a radiate fibrous structure. Structure Under the microscope the spherulites are of circular outline and are composed of thin divergent fibers that are crystalline as verified with polarized light. Between crossed Nicols, a black cross appears in the spherulite; its axes are usually perpendicular to one another and parallel to the crosshairs; as the microscope stage is rotated the cross remains steady; between the black arms there are four bright sectors. This shows that the spherulite consists of radiate, doubly refracting fibers that have a straight extinction; the arms of the black cross correspond to those fibers that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recrystallization (geology)
In geology, solid-state recrystallization is a metamorphic process that occurs under high temperatures and pressures where atoms of minerals are reorganized by diffusion and/or dislocation glide. During this process, the physical structure of the minerals is altered while the composition remains unchanged. This is in contrast to metasomatism, which is the chemical alteration of a rock by hydrothermal and other fluids. Solid-state recrystallization can be illustrated by observing how snow recrystallizes to ice. When snow is subjected to varying temperatures and pressures, individual snowflakes undergo a physical transformation but their composition remains the same. Limestone is a sedimentary rock that undergoes metamorphic recrystallization to form marble, and clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithophysa
A lithophysa (plural lithophysae, from Greek ''lithos'' "stone" + ''phusa'' "bubble") is a felsic volcanic rock with a spherulitic structure and interior cavity with concentric chambers. Its outer shape is spherical or lenticular. They vary in size from very small up to twelve feet in diameter depending on the age of the magma chamber. These rocks are usually found within obsidian or rhyolite lava flows. Lavas low in feldspar minerals may produce a version known as snowflake obsidian. These cavities are believed to be caused by expanding gases in tuffs and rhyolitic lavas before solidification. If the cavity becomes lined with crystals it may be referred to as a geode or if filled partially or fully with agate, jasper or opal it is called a thunderegg. The term vug is also used for similar cavities although the meaning of vug is usually restricted to cavities in rocks formed by the removal of material such as soluble minerals. These cavities usually contain layers of various ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as ''tuffaceous'' (for example, ''tuffaceous sandstone''). A pyroclastic rock containing 25–75% volcanic bombs or volcanic blocks is called tuff breccia. Tuff composed of sandy volcanic material can be referred to as volcanic sandstone. Tuff is a relatively soft rock, so it has been used for construction since ancient times. Because it is common in Italy, the Romans used it often for construction. The Rapa Nui people used it to make most of the ''moai'' statues on Easter Island. Tuff can be classified as either igneous or sedimentary rock. It is usually studied in the context of igneous petrology, although it is sometimes described using sedimentological terms. Tuff is often erroneously called t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ameca, Jalisco
Ameca ( "string of water") is a city and municipality, in Jalisco in central-western Mexico. The municipality covers an area of 839.1 km². The city is bisected by the Ameca River which drains to the Pacific Ocean near Puerto Vallarta. It is located approximately 83 km (approximately 50 miles) from the state capital and one of Mexico's largest commercial centers, Guadalajara. The city is also the seat and largest city of the federal sub-division Región Valles, which compromises the municipalities situated on the central valleys of Jalisco. As of 2010, the municipality had a total population of 57,340, and the city a population of 36,156, making it the 15th largest city of Jalisco in terms of population. History In the early 16th century Ameca was the center of the small kingdom of Ameca. This state was conquered by the Spanish in 1524. It was part of the alcaldia mayor of Autlan, New Spain during the Spanish colonial period. The first of the conquerors who arrive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ahualulco De Mercado
Ahualulco de Mercado is a city and municipality, in Jalisco in central-western Mexico. The municipality covers an area of 274 km2. As of 2005, the municipality had a total population of 21,465. Name origin Ahualulco comes from the Nahuatl word ''Ayahualolco'' which means "place of water crowned" or "place around the water." Geography Location Ahualulco de Mercado is located in central Jalisco, at coordinates 20° 37'20" to 20° 46'10" north latitude and 103° 52'00" to 104º 04'30" west longitude. The municipality is bordered on the north by the municipalities of Etzatlán, San Juanito de Escobedo and Tequila, on the east by the town of Teuchitlán, on the south by the municipalities Teuchitlán and Ameca, and on the west by the municipalities of Ameca and Etzatlán. It lies on the road from El Refugio to San Marcos and is the most populous town and tourism in this area. Weather The weather is semi-arid with dry winter and spring, and semi-warm, no well-defined t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sierra De Ameca
Sierra (Spanish for "mountain range" or "mountain chain" and "saw", from Latin '' serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nieves, a mountain range in Andalusia, Spain * Sierra Madre (other), various mountain ranges ** Sierra Madre (Philippines), a mountain range in the east of Luzon, Philippines * Sierra mountains (other) * Sierra Nevada, a mountain range in the U.S. states of California and Nevada * Sierra Nevada (Spain), a mountain range in Andalusia, Spain * Sierra de San Pedro Mártir, a mountain range in Baja California, Mexico * Sierra Maestra, a mountain range in Cuba Other places Africa * Sierra Leone, a country located on the coast of West Africa Asia * Sierra Bullones, Bohol, Philippines Europe * Sierra Nevada National Park (Spain), Andalusia, Spain * Sierra Nevada Observatory, Granada, Spain North America * High Sierra Trail, Calif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
