International standards and resources
The IUGS has developed a set of classification systems for igneous, metamorphic and sedimentary rocks, including lists of approved names. These are available from the British Geological Society (BGS) website. The BGS website also provides information about other rock structures and deposits.
Australian conventions and resources
Australian geologists follow the IUGS classification of rocks.
In Australia, stratigraphic units are named according to agreed conventions overseen by the Australian Stratigraphy Commission. Geoscience Australia maintains a database of formal names.
Petrology is the study of rocks and their formation. Like minerals, rocks are naturally occurring; however, rocks are aggregates, often made up of several minerals or mineral-like substances. For example, the rock granite comprises quartz, feldspar and biotite.
The 3 major groups of rocks are igneous, sedimentary and metamorphic.
Use lower case for the names of rocks or rock groups:
sandstone granite igneous
Rock layers
Did you know? Stratigraphy is the description of rock bodies and their organisation into mappable units.
Rock units can be organised into different categories, using different properties of the rocks. Each stratigraphic category has a number of unit terms. For example, names of lithostratigraphic units are based on the physical characteristics of the rock bodies, such as colour, texture and composition (called lithologic properties). These units include a principal term, such as Group, Formation, Member, Bed or Flow.
Formal names of most stratigraphic units consist of an appropriate geographical name, and a term indicating the kind and rank of the unit. Use initial capitals for all words in a formal name:
Warrawoona Group Cowra Formation Bendigo Zone Hiltaba Suite the Warrawoona Group rocks
but use lower case for informal (generic) and plural references:
The Cowra and Lachlan groups an alluvial formation
Reminder. Initial capitals are used only for formal names. Informal and collective (plural) references to the same item do not need capitals.
