Glendonites are a relatively common feature of the early Permian sedimentary rocks of the Sydney Basin. This sample is part of the collection used for undergraduate teaching at UoN. I am unsure as to the origin of the sample, but given it is in the collection, it has likely come from the type locality at Glendon in the Hunter Valley. Some spectacular examples can be found in outcrop at Pebbly Beach.
Glendonites are an indicator of glacial conditions and grow in seawater at 2-4°C. They initially form as the precipitate ikaite (CaCO₃.6H₂O), which is quite unstable and is later pseudomorphed by replacement phases (usually calcite).