Mount Coot-tha Building Stones

Meta-sedimentary building stone sourced from Mount Coot-tha Quarry.

A few weeks ago, I put up a blog post about a Gold Mine Hike at Mount Coot-tha in Brisbane, Australia. I wrote that the gold was found in meta-sedimentary rocks, but I didn’t show any good pictures of the rocks. This is because the rocks are highly weathered and also mostly covered with vegetation in the area where the hike is located.

This morning I went with my family to the Brisbane Botanic Gardens at Mount Coot-tha and noticed that many of the building stones used throughout the gardens are blue-gray meta-sedimentary rocks that are locally sourced from Mount Coot-tha Quarry. You can still make out the original sedimentary layers in many of these rocks, which are hornfels metamorphic grade. They were cooked by the intrusion of the Enoggera Granite. The meta-sedimentary rocks make lovely and also very durable building stones. They also make good road aggregate. Here are a couple of pictures of them in use in the gardens:

Decorative wall made out of meta-sedimentary rocks from Mount Coot-tha Quarry.

Another picture of the deocrative wall leading to the Tropical Display Dome building.

Building stones sourced from Mount Coot-tha Quarry are used as decorative building stones in many places throughout Brisbane. I’ll share more pictures in another blog post in future.

What about the gold associated with these rocks? Well, I bet that if you analyzed the rocks in the above wall they would have elevated gold concentrations compared to typical meta-sedimentary rocks. However, their gold concentrations would not be that elevated. The gold grades in these Mount Coot-tha rocks are known to be low and patchy — that’s why gold mining was intermittent and relatively small-scale on the mountain. And that’s why the rocks are sold as building stones and road aggregate — they have value there, even if they’re not worth processing for gold.

Gold Mine Hike at Mount Coot-tha, Brisbane, Australia

An old gold mining shaft at Mount Coot-tha.

Considering the COVID-19 travel restrictions at the moment, my ability to go on georneys (geological journeys) is very limited at the moment. However, here in Australia we are fortunate that we can still go outside for some recreation, as long as we stay close to home. We live close to Mount Coot-tha, a mountain with a beautiful forest reserve and botanic garden. Most weekends, I go for a hike with my husband and son on Mount Coot-tha. My son is 2 1/2, so we go on short hikes that are somewhere between 2 km and 5 km in total distance. Fortunately, there are plenty of great easy, short hiking trails at Mount Coot-tha.

One of our favorite hikes at Mount Coot-tha is along the Ghost Hole Track, which takes you past some old gold mine workings. At Mount Coot-tha, there is gold mineralization is located in small quartz-rich lenses that are located in meta-sedimentary rocks, specifically in the Bunya Phyllite and the Neranleigh-Fernvale Beds. The gold mineralization at Mount Coot-tha is not spectacular. However, there was intermittent gold mining on the mountain from the 1890s to the 1950s. Today, no gold prospecting or mining is permitted in the forest, but you can take a walk along an easy hiking trail to see an old gold mining shaft and some remnants of mining infrastructure. You can even have a picnic at the “Gold Mine Picnic Area”.

We really enjoy our little hikes through the former gold mining area. The forest is beautiful, and the remnants of gold mining and associated informational signs are interesting. The hike is perfect if you want an easy, but interesting, hike to go on with a toddler.

Below are some pictures of the hiking trail. Click on any of the pictures below to enlarge them.

Map showing the location of the picnic area and hiking trail.

A view of the trail through beautiful open eucalypt forest.

Remnants of a dam used for processing gold.

Another informational sign. Note that “yakka” is Australian slang for “hard work”. This mining certainly sounds like hard work!

Remnants of a wooden bridge used for trams.

The forest is really beautiful at Mount Coot-tha.

If you look up, there are sulphur-crested cockatoos in many of the trees.

You can see some lovely butterflies at Mount Coot-tha at certain times of year. Here’s a Blue Tiger Butterfly.

Admittedly, the gold mining infrastructure is not the most spectacular — there’s not much left. However, with the signs it nevertheless makes for an interesting little hike through a beautiful forest. I highly recommend it for a family hike.

Donate to Help Australia – and I’ll Send You an Aussie Postcard

A mother and baby koala at Australia Zoo. I took this picture a couple of weeks ago during our most recent visit to the zoo.

I moved to Australia last year, and I am very happy and proud to be living in this incredible country.

Recently, my heart has been breaking as I hear about the Australian bushfires, which are catastrophic and have grown much worse over the past couple of weeks. The extreme nature of the fires is no doubt due to climate change, as explained, for example, here and here.

I live in Brisbane, and fortunately I haven’t been very affected by the fires, aside from some days of poor air quality. The fires in the state of Queensland are, fortunately, a little better than they were a few weeks ago.

I have felt very emotional over the past couple of months – and especially over the past couple of days as I read about the fires getting much worse in New South Wales and Victoria. The news of fires ripping through Kangaroo Island also made me very upset. I feel sad and helpless – the scale of the devastation and environmental loss is enormous, monstrous, almost unimaginable. There are ecosystems that may never recover. I mourn the loss of these ecosystems, and I feel despair that the world may not wake up in time to avert more major losses as a result of climate change disasters.

I allowed myself some time to feel sad this weekend. Sometimes that is necessary. Then, I decided that I should try to do something to help, even if it is a very small something.

So, I started a birthday (my birthday is January 12th) fundraiser on Facebook for Australia Zoo, which is a zoo about an hour from Brisbane that does amazing work for animals. They have an incredible animal hospital that has treated thousands of animals affected by bushfires. You may know the zoo because it is owned by Steve Irwin’s family. We have a family pass to the zoo, so my husband and I take our son there often. He loves visiting and seeing all of the animals.

I set an initial goal of raising $500 AUD for the fundraiser, and I’m happy to say that I’ve already raised more than that, thanks to some generous donations from friends and family. However, I would love to raise more. If you have a few dollars to spare, please consider donating. If you do and are willing to message me your address, I’ll mail you a postcard from Australia as a thank you!

In fact, I won’t limit the postcard offer to my Facebook fundraiser, since I know that many people are not on Facebook — and also there are many Australian charities in need of aid right now. If you donate to any wildlife or humanitarian charity that is providing assistance for the Australian bushfires, I’ll send you a postcard. Just leave a comment below saying where you made a donation and then email your address to georneysblog (at) gmail (dot) com.

If you need some ideas of where to donate, there are some in this article. For example, my husband and I recently made a donation to the New South Wales Rural Fire Service, in addition to our donation to Australia Zoo.

If you can’t donate, then please share this post — or the link to my Facebook fundraiser.

I hope that I send many postcards out! It’s one small thing I can do. I still feel sad and overwhelmed by the bushfire news, but I’ll do my one small thing — and hopefully inspire others to do small things as well.

Monday Geology Picture: Travertine Wall

A decorative travertine stone on a the front of a building in Brisbane, Australia.

Wow, the past couple of months have been busy! I spent most of May and June travelling for work. Life has calmed down now, so it’s time to resume my blogging… and try to stick with it a little better for the rest of the year!

To kick off some blogging, here’s a picture of a beautiful decorative travertine stone on the front of a building. I took this picture earlier today when I was walking around downtown Brisbane, Australia. There are quite a few beautiful decorative stones on various buildings in Brisbane… I’ll have to take some more pictures to share.

In this picture, you can see the various layers that were deposited from natural spring waters over time. The layers have been tilted 90 degrees — they would have originally been flat-lying.

Monday Geology Picture: Glass House Mountains, Australia

A shot of part of the stunning Glass House Mountains in Queensland, Australia. Photo taken April 2019.

I have been terribly neglecting my blog this year. However, I have a good excuse: over the past few months I have accepted a new job working as a geologist for Anglo American… and I have moved my family to beautiful Brisbane, Australia. On top of that, I am mother to a young son (18 months old now) and I’m also studying part-time… so, I have my hands very full!

However, now that the chaos of moving is over, I thought I would revive my blog… once again! There is much new geology to see here in our new home country, so I’ll try to share some georneys (geology journeys!) here more regularly!

As a start, here is a picture of the majestic, magical Glass House Mountains in Queensland. These mountains are young (26-27 million year old) volcanic plugs. I’ll blog more about their geology soon! For now, enjoy this teaser shot.

Monday Geology Picture: Kangaroo Point Cliffs, Brisbane, Australia

A view of Kangaroo Point Cliffs, taken from across the river, December 2018.

Happy New Year! I’m going to try to keep up with my “Monday Geology Picture” posts in 2019. I did okay with these in 2018, although I missed some weeks here and there when I was very busy with work or family life.

To start off a new year of pictures, here is a picture that I took during a recent visit to Brisbane, Australia. This picture shows a place known as Kangaroo Point Cliffs. These cliffs are not completely natural but were rather formed by a combination of river erosion and quarrying for stone that was used to make several buildings throughout the city. The geology of the cliffs is quite interesting — the cliffs are comprised of Brisbane tuff, a welded ignimbrite that is Triassic in age. I’ll blog more about these fascinating rocks in future.

Here’s a little more information from a sign located across the river from the cliffs:

Sign with some information on the Kangaroo Point Cliffs. Click to enlarge.

The first paragraph says:

The rocks in the Kangaroo Point Cliffs are the debris of an ash flow from an exploding volcano 220 million years ago. The cliffs have been slowly carved by the river and from the 1820s stone was quarried from the cliffs to build the new Brisbane Town.

Monday Geology Picture: Geology Building at the University of Queensland

Part of the wonderful geology building at the University of Queensland.

Earlier this year I visited The University of Queensland in Australia. For this week’s picture, I’m sharing an image of the lovely geology building at the university. The building is made out of gorgeous sandstone blocks… and there’s a dinosaur mural! And, lower down, check out the stones with the fossil carvings! What a great building. I think this is one of the most lovely and delightful geology buildings that I have ever visited.

Does anyone else have a great geology building at their university? If so please share pictures in the comments.

Monday Geology Picture: Newcastle Coal

A piece of coal in my hand — freshly fallen from an outcrop.

During my recent trip to Australia, I was able to pick a piece of coal off of the ground — something that I’ve never done before. I was in Newcastle, a coal mining region, for a conference. One evening I went for a walk along the beach, where coal seams are visible in outcrop. The picture above shows a piece of coal that I picked up off of the beach walking path. Pretty neat! I’ll blog a little more about Newcastle coal when I have a chance — stay tuned!

Monday Geology Picture: Weathered Sandstone at Cottage Point, Australia

Weathered sandstone exposure at Cottage Point, Australia.

Here’s another picture from my recent trip to Australia. This picture shows a weathered sandstone outcrop that I saw (by kayak!) at a place called Cottage Point. You can see fresh banded sandstone (light in color) underneath a darker weathering rim. Weathering has created some very interesting shapes in this outcrop!

There are quite a few sandstone rocks in the Sydney area. They are frequently used as building stones — for example, the ones I shared in an earlier post.

Monday Geology Picture: A Living Fossil Tree

The majestic Wollemi Pine — it certainly looks like a tree that grew during the time of the dinosaurs! And it did grow at that time!

Today is my last day in Australia. Today, my family, some friends, and I spent a few hours exploring the Royal Botanic Garden in Sydney. There are many beautiful and amazing plants in the garden. However, one plant in particular caught my eye: the Wollemi Pine, which is considered a living fossil because until the tree was discovered in the 1990s it was only known from the fossil record. The Wollemi Pine is critically endangered, with only few wild trees remaining in remote sandstone gorges located about 150 km outside of Sydney. While wild trees are uncommon, cultivated trees have become fairly common. In fact, you can buy your very own Wollemi Pine tree in the garden gift shop. I didn’t buy one because I live in South Africa, but if you’re in Australia you should consider buying one to add to your garden.

Here’s a sign board with a little more information about the tree: