Hydrates of mixed crystals of mineral components rather

Hydrates
are composed with water of crystallization in their structures. When a hydrate
is exposed to heat, it absorbs enormous quantity of heat (endothermic) and
forms anhydrous mineral. When an anhydrate is immersed into water; it absorbs
water and releases huge quantity of heat transforming into a hydrate mineral 6.
In other way, it can be expressed that a hydrate is formed by releasing
enormous quantity of heat from its anhydrous product. For an example; the
formation snow from freezing water releases heat and snowfalls warms up the
atmosphere may be cited. The heat released into the pore space might promote
further evaporation of pore fluids. Most of the hydrates are stable and soluble
in water at room temperature. Some hydrates spontaneously loss water of
crystallization by efflorescence. Others absorb water into their structure
forming hydroscopic hydrates. Some deliquescent mineral like sodium hydroxide
absorb huge quantities of water and form as liquid. The decomposition of
carbohydrates generally releases water. Thus water of crystallization in a hydrate
minerals play critical role on their changes in their specific gravities and in
turning their volumes 7. Hydration is not a reversible reaction;
however, the environment crystallization of hydrates plays critical role for
the formation of hydrates and anhydrates 8. 
The repeated hydration and dehydration changes the volume of saline
minerals which in turn affects the volume of pore spaces and hairline cracks
are induced. Most pores are partially or completely filled with saline pore
fluids and repeated influxes of saline fluids and evaporations play critical
role on the evolution of saline precipitates 9.  The evaporation of saline fluids precipitates
saline minerals initially at peripheral portions of saline droplets inside the
pores. The ionic components of chloride, carbonate and sulphate, hydroxide and
water play critical role in the formation of mixed crystals of mineral
components rather than individual minerals. The scope of the investigation
mainly lies to trace the trend of changes of chemical composition during
successive crystallization of chloride components from the primary carbonate
source. Generally, the composition of groundwater is enriched with bicarbonates
and depleted in carbonates. Similar condition is true in the case of saline
waters interlocked in the pore spaces of lime-mortars.