In a method of synthesizing a mostly CHA-type silicoaluminophosphate 
sieve, a reaction mixture comprises sources of water, 
silicon, aluminum, 
phosphorus, and a template. In one aspect, the 
inorganic phosphorus and 
silicon sources are first combined to form a primary mixture that is aged. Then, the aluminum source is added, followed optionally by any 
organic phosphorus source, and then the template, to form the synthesis mixture. After heating at <10° C. / hr to induce 
crystallization, in this aspect, both the crystallized 
sieve has an average 
crystal size ≦1.5 μm and / or is recovered in a yield of ≧10.0 wt %. In another aspect, when the synthesis mixture Si / Al2 ratio is <0.33, 
crystallization is induced. Advantageously, the 
sieve so crystallized has a template efficiency of ≧0.5 and / or is recovered in a yield of ≧10.0 wt %. The 
molecular sieve from both aspects can be used in a 
hydrocarbon (oxygenates-to-olefins) conversion process.