|
Gypsum Caves
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk chalk. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison. Fine-grained white or lightly tinted forms of gypsum known as alabaster have been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England. Etymology and history The word ''gypsum'' is derived from the Greek word (), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became kn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfate Mineral
The sulfate minerals are a class of minerals that include the sulfate ion () within their structure. The sulfate minerals occur commonly in primary evaporite depositional environments, as gangue minerals in hydrothermal Vein (geology), veins and as secondary minerals in the Redox, oxidizing zone of sulfide mineral deposits. The Chromate ion, chromate and manganate minerals have a similar structure and are often included with the sulfates in mineral classification systems.Klein, Cornelis and Cornelius S. Hurlbut, 1985, ''Manual of Mineralogy,'' 20th ed., John Wiley and Sons, New York, pp. 347–354 . Sulfate minerals include: *Anhydrous sulfates **Barite BaSO4 **Celestite SrSO4 **Anglesite PbSO4 **Anhydrite CaSO4 **Hanksite Na22K(SO4)9(CO3)2Cl *Hydroxide and hydrous sulfates **Gypsum CaSO4·2H2O **Chalcanthite CuSO4·5H2O **Kieserite MgSO4·H2O **Starkeyite MgSO4·4H2O **Hexahydrite MgSO4·6H2O **Epsomite MgSO4·7H2O **Meridianiite MgSO4·11H2O **Melanterite FeSO4·7H2O **Antlerite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evaporite
An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of water such as lakes. Evaporites are considered sedimentary rocks and are formed by chemical sediments. Formation Although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen, the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a small drainage basin fed by a limited input of water. When evaporation occurs, the remaining water is enriched in salts, and they precipitate after the water becomes saturated. Depositional environments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medieval England
England in the Middle Ages concerns the history of England during the Middle Ages, medieval period, from the end of the 5th century through to the start of the Early modern Britain, early modern period in 1485. When England emerged from the collapse of the Roman Empire, the Economy of England in the Middle Ages, economy was in tatters and many of the towns abandoned. After several centuries of Germanic immigration, new identities and cultures began to emerge, developing into kingdoms that competed for power. A rich Anglo-Saxon art, artistic culture flourished under the Anglo-Saxons, producing Epic poetry, epic poems such as ''Beowulf'' and sophisticated metalwork. The Anglo-Saxons converted to Christianity in the 7th century, and a network of monastery, monasteries and convents were built across England. In the 8th and 9th centuries, England faced fierce Viking attacks, and the fighting lasted for many decades. Eventually, Wessex was established as the most powerful kingdom and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nottingham Alabaster
Nottingham alabaster is a term used to refer to the English sculpture industry, mostly of relatively small religious carvings, which flourished from the fourteenth century until the early sixteenth century. Alabaster carvers were at work in London, York and Burton-on-Trent, and many probably worked very close to the rural mines, but the largest concentration was around Nottingham. This has led to all the English medieval output being referred to as "Nottingham alabaster". Alabaster, a mineral composed of gypsum and various impurities, is much softer and easier to work than marble and a good material for mass production, though not suitable for outdoor use. Carvings were made as single figures, assemblies for tomb monuments, including full length effigies, but the most common survivals are panels, up to about 20 inches or 50 cm high, from sets for altarpieces, which could be transported relatively easily, and fitted into a locally made architectural surround of stone or wood ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Byzantine Empire
The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived History of the Roman Empire, the events that caused the fall of the Western Roman Empire in the 5th centuryAD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'. During the early centuries of the Roman Empire, the western provinces were Romanization (cultural), Latinised, but the eastern parts kept their Hellenistic culture. Constantine the Great, Constantine I () legalised Christianity and moved the capital to Constantinople. Theodosius I, Theodosius I () made Christianity the state religion and Greek gradually replaced Latin for official use. The empire adopted a defensive strategy and, throughout its remaining history, expe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Rome
In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC), the Roman Republic (50927 BC), and the Roman Empire (27 BC476 AD) until the fall of the western empire. Ancient Rome began as an Italic peoples, Italic settlement, traditionally dated to 753 BC, beside the River Tiber in the Italian peninsula. The settlement grew into the city and polity of Rome, and came to control its neighbours through a combination of treaties and military strength. It eventually controlled the Italian Peninsula, assimilating the Greece, Greek culture of southern Italy (Magna Graecia) and the Etruscans, Etruscan culture, and then became the dominant power in the Mediterranean region and parts of Europe. At its hei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesopotamia
Mesopotamia is a historical region of West Asia situated within the Tigris–Euphrates river system, in the northern part of the Fertile Crescent. Today, Mesopotamia is known as present-day Iraq and forms the eastern geographic boundary of the modern Middle East. Just beyond it lies southwestern Iran, where the region transitions into the Iranian plateau, Persian plateau, marking the shift from the Arab world to Iran. In the broader sense, the historical region of Mesopotamia also includes parts of present-day Iran (southwest), Turkey (southeast), Syria (northeast), and Kuwait. Mesopotamia is the site of the earliest developments of the Neolithic Revolution from around 10,000 BC. It has been identified as having "inspired some of the most important developments in human history, including the invention of the wheel, the planting of the first cereal crops, the development of cursive script, mathematics, astronomy, and agriculture". It is recognised as the cradle of some of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Egypt
Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower Egypt were amalgamated by Menes, who is believed by the majority of List of Egyptologists, Egyptologists to have been the same person as Narmer. The history of ancient Egypt unfolded as a series of stable kingdoms interspersed by the "Periodization of ancient Egypt, Intermediate Periods" of relative instability. These stable kingdoms existed in one of three periods: the Old Kingdom of Egypt, Old Kingdom of the Early Bronze Age; the Middle Kingdom of Egypt, Middle Kingdom of the Middle Bronze Age; or the New Kingdom of Egypt, New Kingdom of the Late Bronze Age. The pinnacle of ancient Egyptian power was achieved during the New Kingdom, which extended its rule to much of Nubia and a considerable portion of the Levant. After this period, Egypt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sculpture
Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sculptural processes originally used carving (the removal of material) and modelling (the addition of material, as clay), in stone, metal, ceramic art, ceramics, wood and other materials but, since Modernism, there has been almost complete freedom of materials and process. A wide variety of materials may be worked by removal such as carving, assembled by welding or modelling, or Molding (process), moulded or Casting, cast. Sculpture in stone survives far better than works of art in perishable materials, and often represents the majority of the surviving works (other than pottery) from ancient cultures, though conversely traditions of sculpture in wood may have vanished almost entirely. In addition, most ancient sculpture was painted, which h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alabaster
Alabaster is a mineral and a soft Rock (geology), rock used for carvings and as a source of plaster powder. Archaeologists, geologists, and the stone industry have different definitions for the word ''alabaster''. In archaeology, the term ''alabaster'' includes objects and artefacts made from two different minerals: (i) the fine-grained, massive type of gypsum, and (ii) the fine-grained, banded type of calcite.''More About Alabaster and Travertine'': Brief Guide explains the different definitions used by geologists, archaeologists, and the stone trade. Oxford University Museum of Natural History, 2012/ref> Chemically, gypsum is a Water of crystallization, hydrous sulfate of calcium, whereas calcite is a carbonate of calcium. As types of alabaster, gypsum and calcite have similar properties, such as light color, translucence, and soft stones that can be sculpture, carved and sculpted; thus the historical use and application of alabaster for the production of carved, decorative art ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hardness Comparison
A variety of hardness-testing methods are available, including the Vickers, Brinell, Rockwell, Meyer and Leeb tests. Although it is impossible in many cases to give an exact conversion, it is possible to give an approximate material-specific comparison table for steels. Hardness comparison table {, class="wikitable" ! Brinell HB (10 mm Ball, 3000 kg load)!!Vickers Vickers was a British engineering company that existed from 1828 until 1999. It was formed in Sheffield as a steel foundry by Edward Vickers and his father-in-law, and soon became famous for casting church bells. The company went public in 18 ... HV (5 kg)!! Rockwell C HRC (120 degree cone 150 kg)!!Rockwell B HRB (1/16" ball 100 kg)!! Leeb HLDH.Pollok, „Umwertung der Skalen“ (“Conversion of Scales”), Qualität und Zuverlässigkeit, Ausgabe 4/2008. , - , 800, , -, , 72, , -, , 856 , - , 780, , 1220, , 71, , -, , 850 , - , 760, , 1210, , 70, , -, , 843 , - , 745, , 1114, , 68 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scratch Hardness
Scratch hardness refers to the hardness of a material in terms of resistance to scratches and abrasion by a harder material forcefully drawn over its surface. Scratch hardness test or scratch test refers to any of a number of methods of measuring scratch hardness. Resistance to abrasion is less affected by surface variations than indentation methods. Scratch hardness is measured with a sclerometer. Attempting to scratch a surface to test a material is a very old technique. The first ''scientific'' attempt to quantify materials by scratch tests was by mineralogist Friedrich Mohs in 1812 (see Mohs scale)."Mohs hardness" in ''Encyclopædia Britannica Online'' The Mohs scale is based on relative scratch hardness of different materials; with |
