When relating to Encyclopedia one can come across the following definitions of crystal:
"mineral, transparent form of quartz, that has crystalline structure and is
characterized by flat facets",
"high quality, transparent, colorless glass".
First definition clearly points onto rock crystal which is depicts artificial high quality glass.
mined from the Nature, the second one
In the end of 17th century in Italy France and Spain people began decorating
chandeliers with rock crystal stones which they cut and polished by hand.
The tradition of crystal chandeliers was adopted by Austrian Monarchy who started
to form the trends in this field with the time and developed it's own special style "Maria-Theresia", which is still being actual.
Those times Bohemia (former Austria, now Czech and Slovak Republics) was a center of crystal making.
With the development of craftsmanship and manufacturing people learned how
to make high quality glass which could be cut and polished and than compete with rock
crystal in transparency and edges evenness. This high quality glass is now most often called crystal.