  One of the still viable candidates for the dark matter is the so-called
mirror matter. Its cosmological and astrophysical implications were widely
studied in many aspects, pointing out the importance to go further with
research and refine the studies. In particular, the Big Bang nucleosynthesis
provides a strong test for every dark matter candidate, since it is well
studied and involves relatively few free parameters. The necessity of accurate
studies of primordial nucleosynthesis with mirror matter has then emerged. In
order to fill this lack, I present here the results of accurate numerical
simulations of the primordial production of both ordinary nuclides and nuclides
made of mirror baryons, in presence of a hidden mirror sector with unbroken
parity symmetry and with gravitational interactions only. These elements are
the building blocks of all the structures forming in the Universe, therefore
their chemical composition is a key ingredient for astrophysics with mirror
dark matter. The production of ordinary nuclides show differences from the
standard model for a ratio of the temperatures between mirror and ordinary
sectors x = T'/T > 0.3, and they present an interesting decrease of the
abundance of 7Li. For the mirror nuclides, instead, one observes an enhanced
production of 4He, that becomes the dominant element for x < 0.5, and much
larger abundances of heavier elements.
