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Your specimen could be either marble or quartzite. Both
are metamorphic rocks which formed during the recrystallisation of different
parent rocks.
Marble forms when limestone is put under intense heat and pressure (usually
during mountain building or where tectonic plates meet). The limestone
recrystallises, destroying any fossils that were present in the original rock.
Marble is often white, but can be other colours according to the impurities
present, and is often used as a decorative stone in buildings or to create
statues.
Quartzite is formed when sedimentary rocks made up of
quartz (often sandstones which are very quartz rich) are heated and
recrystallise. Quartzite is made up of tightly interlocking grains of quartz and
any structures in the rock, such as bedding (visible layers or sediment which
were laid down in beds) are usually destroyed. One way to tell if your rock is
marble or quartzite is to drop some dilute hydrochloric acid (available in rock
and mineral shops) onto it: marble fizzes but quartzite doesn't.
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