The Glass House Mountains are intrusive plugs—remnants of volcanic activity that occurred approximately 25–27 million years ago. Molten rock-filled small vents or intruded as bodies beneath the surface and solidified into hard rocks—trachyte and rhyolite.

Please be considerate of the traditional owner, the Gubbi Gubbi/Kabi Kabi & Jinibara peoples, who hold the peaks in the glasshouse mountains sacred and ask that people don't ascend the summits of Beerwah and Tibrogargan. In light of this there are plenty of options that don't utilize the high cliffs and summits of those mountains for your consideration.  

Follow link for maps/ conditions/ wildlife/ trails, etc:

https://parks.des.qld.gov.au/parks/glass-house-mountains/

West off the Bruce Highway