Historical information

This specimen was recovered from Ceres West of Geelong, Victoria. Greenstone is the name for any metamorphosed basic igneous rock (in the case of this specimen, Gabbro) that gains its greenish colour to the presence of the minerals chlorite, actinolite, or epidote, hence the term 'green' and 'stone'. Greenstone is often formed through metamorphsis along a convergent plate boundary.

In the rock cycle (the series of processes that creates the various types of rocks) there are identified three different types of rocks, which are the sedimentary, the igneous and the metamorphic. Metamorphic rocks started out as sedimentary, igneous or earlier metamorphic rocks but changed from their original condition under the effect of high heat, high pressure or hot, mineral-rich fluid. However, if pressure or heat is too high, then the rock will melt, resulting in the formation of an igneous rock. The name used to describe these types of rocks reflects this specific inherent trait of change, since the word “metamorphic” derives from the Greek word “metamorphosis”, meaning “change of form or structure”. Metamorphic rocks form in the Earth`s crust but can be also found on the surface, due to elevation of the Earth`s surface. They are divided into two categories: the foliated metamorphic and the non-foliated metamorphic rocks.

Significance

Gabbro is a highly useful mineral that is often polished to create cemetery markers and kitchen benches. It is notable for its qualities of durability, being able to withstand extreme elements and wear. Whilst not rare, Gabbro is of great utility and has been highly desirable for its qualities.

This specimen is part of a larger collection of geological and mineral specimens collected from around Australia (and some parts of the world) and donated to the Burke Museum between 1868-1880. A large percentage of these specimens were collected in Victoria as part of the Geological Survey of Victoria that begun in 1852 (in response to the Gold Rush) to study and map the geology of Victoria. Collecting geological specimens was an important part of mapping and understanding the scientific makeup of the earth. Many of these specimens were sent to research and collecting organisations across Australia, including the Burke Museum, to educate and encourage further study.

Physical description

Greenstone is a solid hand-sized metamorphic mineral of a green colour.


Greenstone is the name for any metamorphosed basic igneous rock (in the case of this specimen, Gabbro) that gains its greenish colour to the presence of the minerals chlorite, actinolite, or epidote, hence the term 'green' and 'stone'. Gabbro is a medium to coarse grained rocks that consist primarily of plagioclase feldspar and pyroxene. Greenstone is often formed through metamorphsis along a convergent plate boundary. Gabbro forms due to cooling and crystallization of magma underneath Earth's surface.

Inscriptions & markings

Greenstone/Gabbro/from Ceres west/of Geelong. Has old Geological Survey label/and probably collected by/Richard Daintree in 1861/C.Willam 15/4/21/

Other label:
62 /