A lyotropic ferrocolloid is synthesized by mixing of a cationic ferrofluid and potassium laurate/1-decanol/water ternary solution. Conditions of existence of a nematic phase in this mixture, other mesophases, and their phase diagrams in the vicinity of the nematic one are obtained and characterized quantitatively. Inside of the nematic zone the lyotropic ferrocolloid becomes a ferronematic, i.e., a liquid crystal with remarkably strong magnetic properties. We found that the pH and the component concentrations dramatically affect the amount of magnetic particles stably suspended in a lyotropic carrier. Magnetization and magnetic susceptibility of synthesized ferronematics are measured depending on the concentration of dispersed magnetic particles.