Kwartsiet: verschil tussen versies
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Regel 5:
Zandsteenkwartsiet bestaat in twee typen met verschillende geologische processen maar wel vrijwel dezelfde chemische samenstelling:
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'''''quartzite''' A metamorphic rock composed mainly of quartz and usually formed by the metamorphism of quartz sandstones. If deformation has accompanied metamorphism the individual quartz crystals are elongate and take on a preferred orientation, defining a planar or linear fabric within the rock. Unmetamorphosed sedimentary quartzites (sandstones with a quartz cement) are known as 'orthoquartzites' to distinguish them from metamorphic quartzites (metaquartzites).''</ref>
'''''quartzite''' (1) A granoblastic metamorphic rock consisting mainly of quartz and formed by recrystallization of sandstone or chert by either regional or thermal metamorphism; metaquartzite. Cf: orthoquartzite.''
''(2) A very hard but unmetamorphosed sandstone, consisting chiefly of quartz grains that have been so completely and solidly cemented with secondary silica that the rock breaks across or through the grains rather than around them; an orthoquarizite. The cement may grow in optical and crystallographic continuity around each quartz grain, thereby tightly interlocking the grains as the original pore spaces are filled. Skolnick (1965) believed that most sedimentary quartzites are compacted sandstones developed by pressure solution of quartz grains. The term is also used for a metamorphic rock produced by recrystallization of a sandstone.'' en verderop:
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