We report that the composition of La 1 . 2 Ca 1 . 8 Mn 2 O 7 does not form as a single phase, and consists of a mixture of La 0 . 6 Ca 0 . 4 MnO 3 and CaO. The XRD patterns show the presence of a peak at 2θ ~ 37 o , which is a specific peak to indicate the existence of CaO with space group Fm3m and a unit cell of a = 4.8152(3) Å. After a few days, the intensity of this peak decreases and CaO transforms to Ca(OH) 2 . The electrical and magnetic measurements show that the colossal magnetoresistance (CMR) behavior corresponds to that exhibited by La 0 . 6 Ca 0 . 4 MnO 3 .