score:3
No, it's never been miraculous.
Paper burns with a light-coloured smoke, so to produce white smoke just the ballot papers are burned. To produce black smoke, it used to be the case that damp straw was added but that was also capable of producing smoke which didn't look black.
AP reports that for the 2005 conclave (which elected Benedict XVI) the Holy See introduced a second stove which produced coloured smoke. The ballot papers were burned, but the colour was chemically produced in order that it was unmistakeable.
Judging by the first emission of black smoke, which was clearly black even in the evening, it would appear that this chemical method is in use for the current conclave too.
Picture from AP reproduced on The Blaze blog