Black Perry
Black Perry contains a rare 'skarn' deposit, which formed when molten rock came in contact with limestone, 'cooking' it at more than 580°C. This changed the chemistry and composition of the rock and resulted in the formation of rare minerals, such as babingtonite and hedenbergite, which has only been recorded in a few other places in the world.
The skarn deposits of Black Perry are more resistant to erosion than the adjacent rock types, hence Black Perry protrudes in an area that has otherwise been heavily eroded.
On the lower slopes of Black Perry, limestone was exposed to less instense heat and turned into marble rather than skarn. The subsequent action of water dissolving and eroding weaker sections of rock has resulted in the formation of small caves.
- sign at GZ by NSW National Parks and Wildlife Service
As indicated above, little old Black Perry is a pretty unique mountain. These skarns contain the first known occurrence of babingtonite in Australia. There are only six localities in the world where babingtonite is present in skarns.
What is Babingtonite?
Babingtonite is a calcium iron manganese inosilicate mineral (any of a class of inorganic chemical compounds that have structures characterized by silicate tetrahedrons). It is unusual in that iron completely replaces the aluminium so typical of silicate minerals.
Questions
At GZ is a lookout where you can take in the tranquility and beauty of the area, including Black Perry, while you consider the following questions. Answers should be sent by private message. Please do not include your answers in your log.
- Identify Black Perry from the vista in front of you. There is a sign at GZ which can assist with this but Black Perry is located to your right, just tucked in behind a foothill and it is very distinctive from the rest of the landscape. Describe Black Perry and what makes it so distinctive.
- In your own words, how do you think Black Perry was formed?
- Why do you think Black Perry has not eroded as the surrounding landscape has?
- What makes Black Perry so unique?
- (Optional) Please include a photo of yourself or your GPSr at GZ with Black Perry behind you.
Please feel free to log your find without waiting for an answer. I will contact you if there are any problems with your answers.
References:
Ca-Fe-Si Skarns Containing Babingtonite: First Known Occurrence in Australia by M.J. Gole, retrieved from https://www.researchgate.net/publication/266530860_Ca-Fe-Si_SKARNS_CONTAINING_BABINGTONITE_FIRST_KNOWN_OCCURRENCE_IN_AUSTRALIA on 8 July 2018
Babingtonite, retrieved from https://en.wikipedia.org/wiki/Babingtonite on 8 July 2018