Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?

Refractive index of a solid is observed to have the same value along all directions . Comment on the nature of this solids . Would it show cleavage property ?

The physical property (ies) which (is) are same along all the directions in an isotropic solid-

If refractive indedx is found to be same in all directions through a solid, then this propery is called ______

Thermal conductivity of a solid has different values along different directions. What kind of solid is this ? Also comment on its melting point .

Thermal conductivity of a solid has different values along different directions. What kind of solid is this ? Also comment on its melting point .