  This paper proves that from the algebraic point of view ELKO spinor fields
belong together with Majorana spinor fields to a wider class of spinor fields,
the so-called flagpole spinor fields, corresponding to the class 5, according
to Lounesto spinor field classification. The main algebraic difference between
ELKO and Majorana spinor fields is that in the first case their respective two
2-component spinor fields present opposite helicities, while in the second case
the helicity associated with the two 2-component of ELKO are not imposed to be
flipped. The proof of our statement is based on Lounesto general classification
of all spinor fields, according to the relations and values taken by their
associated bilinear covariants, and can shed some new light on the algebraic
investigations concerning dark matter.
