The strongly correlated quantum spin liquid (SCQSL) is a specific realization of a possible quantum spin liquid (QSL) representing a new type of strongly correlated electrical insulator (SCI) that possesses properties of heavy fermion metals with one exception: it resists the flow of electric charge. At low temperatures T the specific heat of this type of insulator is proportional to T, with n less or equal 1 rather than n =3, as it should be in the case of a conventional insulator whose heat capacity is proportional to T. When a magnetic field B is applied to SCI the specific heat depends strongly on B, contrary to conventional insulators. There are a few candidates of SCI; the most promising among them is Herbertsmithite, a mineral with chemical structure ZnCu 3 (OH) 6 Cl 2.