This section is from the book "Modern Chemistry", by William Ramsay. Also available from Amazon: Modern Chemistry: Theoretical and Modern Chemistry (Volume 2).
Metasilicates are derivatives of the acid H2SiO3; the constitutional formula is 0=Si(OH)2, like that of carbonic acid. Examples of metasilicates are:-

Wollastonite.

Augite or Hornblende.

Jade.
The potassium salt is Leucite.
 
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