Thursday, 31 May 2018

Montepuez ruby deposit, Mozambique - Gemfields (LON:GEM)

The Montepuez ruby deposit is located in the northeast of Mozambique in the Cabo Delgado province. Covering approximately 33,600 hectares, it is the most significant recently discovered ruby deposit in the world. Precious stones miner Gemfields confirmed its Montepuez ruby mine in Mozambique has enough reserves to last at least 20 years.

Estimates of probable ore reserves are 432 million carats at a diluted grade of 15.7 carats per tonne over 21 years.
Less than 10 years after discoveries near Montepuez in 2009, rubies from Mozambique have taken a major place in the trade. Gemfields held its first rough ruby auction in June 2014. In 2016, mining for gemstones or gold without a license became a crime punishable by three years in jail. In 2017 the government targeted buyers. Police operations were launched and many foreign buyers were arrested, fined, and expelled. Gemfields later had its most successful ruby auction ever in June 2017, recording more than US$54 million in sales.
The concession is located at a geologically critical junction between the north-south trending Mozambique Belt and the east-west trending Zambezi Belt. Primary rubies are formed when fluid derived from the parental magma interacted with the host rocks under a silica unsaturated environment.

After hundreds of millions years of erosion, rubies are liberated from the host rock and transported and concentrated by water and eventually settled in alluvial, colluvial, and eluvial deposits.
In November 2016 Gemfields discovered a 40.23-carat ruby at Montepuez which it has called “one of the most important rubies unearthed in recent times” While the yield from the rough depends on a number of factors, including the shape, inclusions, and the nature of the crystal. With a yield of 30 percent to 40 percent one should get a 12 to 16 carat gem.
The important question would be how clean the stone is and whether or not it requires heat treatment. A clean stone without heat treatment is far more valuable.

If this is the case, the piece of rough could yield a cut and polished ruby with a wholesale value of $1.5 million or more. The stone is significant because it attests to the mine’s ability to produce important rubies. Due to the rarity of rubies, the discovery of a 40-carat ruby is comparable to finding a 100-carat rough diamond.