Which is known as crystal carbonate?

$\underset{\mathrm{white} \mathrm{crystalline} \mathrm{solid}}{{\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}}\underset{-9{\mathrm{H}}_2\mathrm{O}}{\overset{<{100}^0\mathrm{C}}{\to }}{\mathrm{Na}}_2{\mathrm{CO}}_3.{\mathrm{H}}_2\mathrm{O}\underset{-{\mathrm{H}}_2\mathrm{O}}{\overset{>{100}^{\mathrm{o}}\mathrm{C}}{\to }}\underset{\mathrm{soda} \mathrm{ash}}{{\mathrm{Na}}_2{\mathrm{CO}}_3}$

Sodium carbonate crystallises as sodium carbonate decahydrate on heationg below 100°C, it loses 9 molecules of water of crystalliisation to from monohydrate [Na₂CO₃.H₂O]