Hi.
Please see Section 1.1 Defining Report Content of GRI G3 Guidelines (2006);see the section on Materiality under 1.1. That will answer your question.
For those readers, who are not familiar with GRI G-3 Guidelines, here is the link: http :// www. globalreporting.org/NR/rdonlyres/B52921DA-D802-406B-B067-4EA11CFED835/3882/G3_GuidelinesENU.pdf - BROKEN LINK UNLINKED
With kind regards,
Ramakrishnan