The Wonders of Garnet From Broken Hill, NSW, Australia.
Last week this epic Garnet specimen took up residence inside the Crystal World Exhibition Centre. In October 2023, this garnet was mined by our staff in Broken Hill, originally weighing in at about 2 tonne, it’s an absolute wonder. For this particular mining venture our team was joined by Rod Manning and JC and will be featured on Opal Hunters: Red Dirt Road Trip. We personally can’t wait until it airs in Australia !
Now let's jump in and explore the wonders of Garnet From Broken Hill, Australia.
Geological Setting and Composition
Garnet, a gemstone that has captivated humanity for centuries, is not only prized for its beauty but also for the secrets it holds about Earth’s geological past. The garnet specimens from Broken Hill, New South Wales, Australia, are particularly renowned for their unique composition and the insights they provide into metamorphic processes.
Broken Hill is home to the Willyama Complex, a region that has undergone extensive metamorphism. The garnets found here are embedded in finely bedded banded iron formations (BIFs). These garnets exhibit remarkable compositional changes on an ultra-fine scale, which is not attributed to variations in metamorphic conditions but rather to the original rock composition.
Metamorphic Indicators : The composition of garnet in this region serves as an indicator of the premetamorphic physicochemical conditions. Studies suggest that the garnet-rich rocks of the Proterozoic southern Curnamona Province, where Broken Hill is located, are metamorphosed chemical precipitates formed on the floor of a continental rift basin.
Rare Earth Element (REE) Patterns : Garnet from Broken Hill is characterized by light rare earth element (LREE) depletion and heavy REE (HREE) enrichment with distinct Eu anomalies. These patterns provide clues to the nature of the hydrothermal fluids and the physicochemical conditions during the formation of the precursor minerals.
Geochemical Signatures: The garnet-rich rocks from Broken Hill are distinguished by their higher average contents of Mn, K, Rb, Eu, Ga, Cs, Cu, Pb, Zn, As, Cd, Sb, Ag, W, and Au compared to other locations. This geochemical signature indicates a larger hydrogenetic component to their precursor minerals.
Mineralization and Economic Significance The garnet mineralization at Broken Hill is not only of academic interest but also of economic significance. The presence of almandine garnet, in particular, is associated with a narrow zone of abundant mineralization, where crystals can reach impressive sizes and weights.
Garnet Uses
Garnet from Broken Hill is used for both gemstones and industrial purposes. Here’s a detailed breakdown of its uses:
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Gemstones: The garnet varieties found in Broken Hill can be of gemstone quality, which are used in jewelry and ornaments. They are appreciated for their color and clarity.
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Industrial Uses: Almandine garnet, which is common in the deposits around Broken Hill, is particularly important for industrial applications. It’s used as an abrasive due to its hardness and resistance to weathering. This makes it suitable for products like sandpaper and in waterjet cutting. Additionally, garnet’s durability allows it to be used as a skid-resistant road aggregate, in skid-resistant paints, and as a filler in concrete for harsh environments2.
The Thackaringa district near Broken Hill has extensive areas of garnet-bearing metamorphic rocks, and mines have operated there intermittently since the 1960s, highlighting the significance of this mineral in the region.
References :
- Oxford Academic Journal of Petrology
- Mineralogy and Petrology:
- GeoScienceWorld Economic Geology
- The Australian Museum