A silicate is an SiO2-centric solid (crystalline or glass). A borosilicate simply is a silicate with boron. The term 'borosilicate' is synonymous with medium and low fire glazes because boron is not employed at high temperatures (CaO, Na2O, MgO, etc flux silica and bond with it to form crystalline or glass solids on cooling). The term 'borosilicate' almost always refers to a frit in ceramics. Such frits may have 5% B2O3 or 50%, but they always have plenty of SiO2 so the two can combine, and with other oxides in the melt, form silicates. Since boron is the melter that makes the glaze or glass possible, terminology referring to the chemistry normally mentions it.
|Glossary||High Temperature Glaze
|Glossary||Medium Temperature Glaze
These are stoneware glazes that fire in the range of 1200C (2200F). They often contain boron to assist with melting.
Borate glazes, those fluxed with the oxide B2O3, are the most common type used in ceramic industry and hobby for low and medium temperatures.
Frits are used in ceramic glazes for a wide range of reasons. They are man-made materials of controlled chemistry with many advantages or raw materials.
Silicate at Wikipedia