Answer:
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Explanation:
Quartzite
Quartzite is a metamorphic rock formed when quartz-rich sandstone or chert has been exposed to high temperatures and pressures. Such conditions fuse the quartz grains together forming a dense, hard, equigranular rock. The name quartzite implies not only a high degree of induration (hardness), but also a high quartz content. Quartzite generally comprises greater than 90% percent quartz, and some examples, containing up to 99% quartz, and are the largest and purest concentrations of silica in the Earth's crust. Although a quartz-rich sandstone can look similar to quartzite, a fresh broken surface of quartzite will show breakage across quartz grains, whereas the sandstone will break around quartz grains. Quartzite also tends to have a sugary appearance and glassy lustre. The variety of colours displayed by quartzite are a consequence of minor amounts of impurities being incorporated with the quartz during metamorphism. Although quartzite can sometimes appear superficially similar to marble, a piece of quartzite will not be able to be scratched by a metal blade, and quartzite will not fizz on contact with dilute hydrochloric acid.
Texture - granular.
Grain size - medium grained; can see interlocking quartz crystals with the naked eye.
Hardness - hard.
Colour - variable - pure quartzite is white but quartzite exists in a wide variety of colours.
Mineralogy - quartz.
Other features - generally gritty to touch.
Uses - pure quartzite is a source of silica for metallurgical purposes, and for the manufacture of brick; as aggregate in the construction and roading industries; as armour rock for sea walls; dimension stone for building facings, paving etc.
New Zealand occurrences - northwest Nelson (Aorere).
Answer:
mutation in DNA
Explanation:
Mutations are changes in the genetic code that can occur in many ways. Each time a cell divides, say, DNA must be copied into two copies, one copy for each new cell. Although this copying is very precise, it is still not perfect - for about every billion accurately copied databases, one is mistranslated.
Another source is DNA damage, which can occur spontaneously through the normal life of the cell, or through external toxins or negative influences (ultraviolet radiation, for example). Through evolution, cells have developed a very complex system for repairing changes in DNA, but these systems not only have limitations but can sometimes cause additional errors themselves.
Answer:
Almost all of the cells in your body share the same DNA as was found in that first cell. Eyes and heart are so different because different set of problems are made in the various eyes and heart cell
Explanation:
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Answer:
Persistent depressive disorder.
Persistent depressive disorder, known as dysthymia or low-grade depression, is less severe than major depression but more chronic. It occurs twice as often in women as in men. Persistent depressive disorder (PDD) is a serious and disabling disorder that shares many symptoms with other forms of clinical depression.
