Zeolites having CHA framework structure and a composition comprising the molar ratio (n SiO2): X203, wherein X is a trivalent element, and wherein n is at least 10, wherein the crystal size, as determined from Scanning Electron Microscopy, is greater than 1 micrometer and wherein the chabazite framework is phase-pure having an impurity of other zeolitic frameworks, such as RUT 25 as determined by X-ray Diffraction, of less than 5%. The process for the preparation comprises:(i) preparation of an aqueous solution containing at least one source for X203 , wherein X is selected from Al, B, Ga, and a mixture of two or more, and at least one source for SiO2, at least one organic structure directing agent (SDA) other than Tetramethylammonium hydroxide (TMAOH), acting as a template for the CHA structure, and Tetramethylammonium hydroxide (TMAOH), wherein the SDA or mixtures thereof are employed in such amounts that the aqueous solution in (i) exhibits a molar ratio of SDA : TMAOH of 0.01 to 5;(ii) hydrothermal crystallization of the aqueous solution according to (i); wherein the aqueous solution of (i) contains copper in an amount less than 0.005 Cu:((n YO2)+X203) where n is in the range of 10 to 50.