In general if two compounds are isostructural then a solid solution will exist between the end members (also known as patents). For example sodium chloride and potassium chloride have the same cubic crystal structure so it is possible to make a pure compound with any ratio of sodium to potassium (Na1-xKx)Cl by dissolving that ratio of NaCl and KCl in water and then evaporating the solution. A member of this family is sold under the brand name Lo Salt which is (Na0.33K0.66)Cl hence why it contains 66% less sodium than normal table salt (NaCl). The pure minerals are called halite and sylvite, a physical mixture of the two is referred to as sylvinite.