The big difference between the press release and the actual article is the focus. The press release focuses entirely upon the Martian applications that the desert varnish has. Whereas the journal article's key point is that the formation of silica gels is more important to desert varnish formation than manganese. The article also makes the argument that organic material can enhance and accelerate the processes through which desert varnish forms (it can also slow it down, if there is too much water though). It also makes ties between silica gel deposits worldwide and those that are currently considered separate phenomena (lumped together as desert varnish).
I guess I understand the reason why the press release emphasizes a facet of the study that was covered in less than 2 sentences, but I still find the whole occurrence bizarre.
Click here for the press release
Click here for the pdf (via geoscienceworld, subscription required)
Click here for the pdf (via geology, subscription required)
Baking black opal in the desert sun: The importance of silica in desert varnish Geology Volume 34, Number 7, July 2006
Randall S. Perry (1),(6), Bridget Y. Lynne (2), Mark A. Sephton (1), Vera M. Kolb (3), Carole C. Perry (4), James T. Staley (5)
(2) Department of Geology, University of Auckland, New Zealand
(3) Department of Chemistry, University of Wisconsin-Parkside, USA
(4) Chemistry Division, Nottingham Trent University, UK
(5) Department of Microbiology, University of Washington, USA
(6) Planetary Science Institute, Washington, USA