Marra Mamba Tiger Eye (supercabs) polishing techniques

In this article, I will delve into the intricacies of Marra Mamba polishing techniques, uncovering the secrets to bringing out the gem’s exceptional beauty and sheen. The Marra Mamba Tiger Eye is a captivating gemstone found in the Pilbara iron ore district during the mid-1970s. Its allure lies in the presence of multiple bands of magnetite, creating a visually stunning display.

Marra Mamba Tiger Eye: discovering the beauty of multiple bands of magnetite

Marra Mamba Tiger Eye was discovered long before Western Australian iron ore extraction mining developed into an international industry. It was unearthed by a select group of prospectors in the Pilbara iron ore district. Collectors and lapidaries worldwide, including myself, actively seek out these exceptional specimens.

Gem rough like the Marra Mamba Tiger Eye is anything but subtle. It catches you by surprise – demanding attention and challenging you to unlock its full potential through brilliant polishing and cutting. However, cutting this stone can be extremely challenging due to its variable hardness (at mm-scale) and the occasionally erratic orientation of the riebeckite mineral. 

The asbestiform nature of riebeckite, combined with its tendency to pull out, feather, and bruise, adds to the difficulty. For decades, gem cutters have been intimidated by the easily worked magnetite alongside the multi-hued jasper that prefers to ‘orange-peel’ rather than shine. And I was no exception.

Marra Mamba Tiger Eye Super Cab displaying multiple bands of magnetite    Marra Mamba Tiger Eye Super Cab displaying multiple bands of magnetite    Marra Mamba Tiger Eye Super Cab displaying multiple bands of magnetite

When a client approached me for an initial assessment of their block of rough tiger eye, I couldn’t help but wonder: “Could it be a piece of the wonderful Marra Mamba with the insanely chatoyant blue/red riebeckite bands running through it?” Upon unwrapping it, I was astonished to see that the piece exceeded all my expectations! It’s exceptionally rare to find such an abundance of fine magnetite layers within just a few centimetres of this exquisite material. The chatoyancy of this Marra Mamba Tiger Eye is truly remarkable, thanks to its breathtaking brightness.

While this particular parcel presented the expected challenges from such a material, my previous experience with similar stock pieces allowed me to plan and overcome each obstacle step by step.

Polishing Marra Mamba Tiger Eye: unveiling radiance in multiple magnetite bands

Although I have previously enjoyed the easy success of polishing the magnetite, I remained frustrated by the beautiful but uneven polish on some sections of jasper within the tiger eye. This uneven polish is known as ‘orange-peeling.’

After meticulous experimentation, I discovered that the appropriate use of a specific set of pre-polish wheels, often diamond in my case, significantly reduced this issue. By finding the right balance of water and pressure, along with ample time on various fine-grade diamond wheels, I successfully achieved a consistent and desired polish across all the jasper material.

Continuing my quest for perfection, I began whittling away at the easier aspects of polishing the riebeckite. The red material responded positively, marking a notable triumph. However, the recalcitrant blue riebeckite proved more challenging, often exhibiting tendencies to pull, feather-cleave, or appear bruised.

Music: “As Leaves Fall” by @iksonmusic

Complicating matters further, the gem’s best material contained these two colours intercalated, making it difficult to polish evenly. Nonetheless, these blue zones frequently produce arresting green and silver elements throughout the gem. By implementing directional sanding, even at the 600 grit stage, and employing effective pre-polishing techniques, I managed to minimise difficulties and create a more streamlined polishing experience. Despite this, the entire polishing process demanded significant patience and meticulous care.