INNOVATION Sept-Oct 2019

F E A T U R E

Remember your first big idea?

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It is these important trace elements that give gems their distinctive colours. For example, different elements present in trace amounts—such as iron, titanium, and chromium—are responsible for corundum’s final color. Blue corundum is known as sapphire, red corundum is known as ruby, and corundum in any other colour, including brilliant yellow, orange, green, and purple, are known as “fancy sapphires.” The rich blue to violet- blue coloured gems are the most desirable. Most of the more common spinel in the samples Groat and Belley collected was purple, but they also sampled at least two occurrences of electric blue spinel. Spinel, said Groat, is becoming more important as a gemstone because traditional sources of gems are being mined out. Ruby red sapphires are becoming increasingly rare and red spinel can look very similar. Spinel formation, however, is less well understood. The few locations producing gem spinel around the world are mostly recovering them from eluvial or alluvial deposits, transported away from the source rocks where they originally formed. A FORMATION STORY EMERGES FROM THE DATA The data gathered from these analyses indicated that certain characteristics of the protolith, or starter rocks, and a specific sequence of pressure and temperature events, are required to make the different gem types. For example, limestones containing lenses of clay or mud may result in sapphire or spinel, depending on the exact composition. But if the original limestone also contained evaporites, or salty layers, within the mud, lapis lazuli will form. “The right mix of elements are necessary to not only form the mineral but also include elements in the right proportions to give them the desired colour,” said Groat, “The spinel, for example, needs cobalt to make the electric blue colour, but not too much iron, because that will spoil the colour at very high concentrations by making the spinel dark in color with grey overtones.” Pressure, temperature, and other forces during growth are also critical to gem formation. Belley discovered that the sapphires likely formed in a “hundred-degree window.” The only location where the limestone would likely undergo these temperatures is a thrust fault structure in the LHG. “That also points to where further exploration should take place,” said Groat. However, the gems must form in a part of the fault where they are protected from the shearing forces of the thrust fault, because when a mineral is sheared, tiny inclusions of fluid are trapped in the gem when it “heals,” degrading the quality. Both Belley and Groat believe that there is untapped potential to find more gems on Baffin Island and the nearby smaller islands, and they plan to continue their research in the area.

The Engineers Canada – Manulife Scholarship

To explore more big ideas, apply for 1 of 3 $12,500 scholarships from Engineers Canada and Manulife.

Eligibility:

n Canadian citizens or permanent residents of Canada n Professional engineers returning to university for further study or research in an engineering field Visit engineerscanada.ca/scholarships for more scholarship details and applications. Deadline to apply: March 1, 2020.

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