I found this and thought you guy's may find it interesting......
Was It An Iron Meteorite? © Robert G. Bauval 2002 Published in
Discussions in Egyptology, Volume 14, 1989 The prevailing theory
on the design of monumental true pyramids is that their shape
was modelled on the Benben: a conical-shaped stone venerated in
the ‘Mansion Of The Phoenix’ at Heliopolis (pyr. 1652). The
‘Mansion Of The Phoenix’ was presumably within the precinct of
the Great Sun Temple of Heliopolis, but there is evidence,
however, that the Benben was worshipped there well before the
sun cult of Ra (Baines, Orientalia 39, 1979, p.391). The stone
was probably originally associated to Atum, a much older deity
who was mainly identified with the act of Creation via his
masturbation (Baines, ibid., p.391, fn.2). Atum was later
assimilated to Ra, as Ra-Atum. Though it is often recognised
that the older, step pyramid design is the product of a
predominant star cult (Edwards, p.292; Badawy, p.205), it is
nevertheless widely advocated that the ‘