The Enigmatic Rainbow Lattice Sunstone from Tomkap Mine
Rainbow Lattice Sunstone is a captivating gemstone known for its unique optical phenomena, including aventurescence and adularescence. These effects are caused by the oriented inclusions of hematite and magnetite, which create a stunning lattice pattern that shimmers with iridescent colours.
The Tomkap Mine: A Hidden Treasure
The Tomkap Mine, owned by Crystal World is located in the Harts Range of the Northern Territory, Australia. It is one of the primary sources of this rare gemstone. This remote area, known for its dry plains and rocky outcrops, provides the perfect environment for the formation of Rainbow Lattice Sunstone. The mine itself is relatively small, covering an area of about 500 by 600 meters.
The Harts Range offers a unique combination of geological conditions that are essential for the formation of Rainbow Lattice Sunstone:
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Geological Composition: The region is rich in feldspar minerals, which are crucial for the formation of sunstones. The presence of orthoclase feldspar, in particular, provides the necessary crystal structure for the lattice patterns to develop.
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Inclusions: The dry plains and rocky outcrops of the Harts Range facilitate the formation of hematite and magnetite inclusions within the feldspar crystals. These inclusions are responsible for the aventurescence and adularescence effects that make Rainbow Lattice Sunstone so unique.
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Tectonic Activity: The area’s geological history includes significant tectonic activity, which has contributed to the formation of the unique lattice patterns. The movement of the Earth’s crust has allowed for the crystallographically oriented exsolution of hematite and magnetite within the feldspar.
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Climate: The arid climate of the Harts Range helps preserve the integrity of the sunstones. The lack of significant rainfall and vegetation reduces the risk of weathering and erosion, ensuring that the gemstones remain intact and retain their unique optical properties.
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Geological Significance
The inclusions within Rainbow Lattice Sunstone are primarily hematite and magnetite. Hematite forms small, yellow to deep orange platelets that create the aventurescence or “sunstone effect,” giving the gems an orange glow. Magnetite forms black, equilateral triangles that contribute to the lattice pattern. These inclusions are the result of crystallographically oriented exsolution crystals within the feldspar crystal.
Let's explore this further:
Crystallographically Oriented means that these newly formed crystals align themselves according to the crystal structure of the host mineral. In feldspar, this alignment follows specific crystallographic planes, which are the natural planes of weakness or symmetry within the crystal structure.
How It Happens in Feldspar
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High-Temperature Formation: Feldspar initially forms at high temperatures deep within the Earth. At these temperatures, different elements (like iron and titanium) are evenly distributed within the feldspar crystal.
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Cooling and Exsolution: As the feldspar cools, it becomes energetically favorable for these elements to separate out and form their own distinct crystals. This process is called exsolution. The separated crystals are typically hematite and magnetite in the case of Rainbow Lattice Sunstone.
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Crystallographic Orientation: The exsolved crystals align themselves according to the crystallographic planes of the feldspar. This means they follow the natural symmetry and structure of the host crystal, creating a regular and predictable pattern.
Resulting Inclusions
These exsolved crystals become inclusions within the feldspar. Because they are crystallographically oriented, they form regular patterns, such as the lattice seen in Rainbow Lattice Sunstone. These inclusions are responsible for the gemstone’s unique optical effects, like aventurescence and adularescence.
Crystal World Australia: Showcasing Natural Wonders
Rainbow Lattice Sunstone is not just a beautiful gemstone; it is a piece of Earth’s history, a natural marvel that tells a story of geological processes and the passage of time. Its rarity and unique optical properties make it a sought-after gem for collectors and enthusiasts alike.
If you ever find yourself in Victoria, a visit to Crystal World Australia is a must. There, you can witness the beauty of Rainbow Lattice Sunstone and explore a world of minerals and fossils that will leave you in awe. We have a significant collection of Rainbow Lattice Sunstone, expertly cut and polished to reveal its full beauty. Crystal Word has crafted some of the finest pieces of this gemstone, highlighting its unique optical properties.
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References:
- Wikipedia
- Crystal World Australia
- link.springer.com