Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Asian rubies come always with marble and salt


Ruby deposits are the primary gem source in Central and South-East Asia. They are highly prized and have a special character: the rubies always occur as inclusions in marble. Geologists from the IRD and CRPG/CNRS (1) have investigated the tectonic and geochemical mechanisms involved in their formation and established a new model of how they generated. It involves feeder fluids resulting from solution of layers of salts present in the marble formations. These hot fluids were brought into circulation at the time of the Himalayan chain orogeny and provided the conditions for mobilization of the constituent elements of ruby and its crystallization within the marble. This genetic model gives the partner countries valuable information on the structure and geochemistry of ruby formations and tools necessary for improved targeting of prospection for this rare and highly sporadic type of mineral concentration.

Ruby is mineralogically the chromiferous variety of corundum gemstone, in other words an aluminium oxide in which some of the aluminium ions have been substituted by chromium. Chromium contributes, along with vanadium, another metal constituent of ruby, to the crystal’s red colour.

The most prized ruby deposits are those of Central and South-East Asia, like in the celebrated Mogok deposit in Myanmar (ex-Burma), from which the highest gem-quality rubies are extracted, reputed for their intense "pigeon blood" colour and their transparency.

In spite of their commercial interest, these deposits have attracted little geological research. However, they possess a special feature that have stimulated the interest of the IRD and CRPG/CNRS scientists for several years. The ruby crystals they hold are always present as inclusions in marble formations, which are calcareous rocks altered by high temperature. Research projects have been launched to determine in particular the origin of certain major constituents of the ruby which are usually absent from marbles--mainly aluminium, chromium and vanadium--, unravel the mechanisms of formation of these deposits, their age and their significance in the functioning of deep zones of the Earth’s crust. Combination of field data and results of laboratory geochemical analyses on samples taken from different deposits recorded from Afghanistan to Viet Nam, the team succeeded in establishing a new genetic model, valid for the whole of these deposits where ruby is associated with marble (2).

Ruby crystals form at high temperature, between 620 and 670°C. Dating of minerals contemporary with their growth, such as zircon and mica, performed in the different deposits gave the age of the ruby crystallization. Depending on the deposits, this was found to be 40 to 5 million years B.P., in the Cenozoic. The ruby is thus an excellent geological marker of the collision between the Indian and the Eurasian plates which set off the Himalayan uplift.

Analysis of liquid inclusions trapped by the rubies during crystallization revealed the participation of feeder fluids riches in salts and carbon dioxide, source of which has been defined by using their chemical composition. They result from the high-temperature solution of salts contained in evaporite-bearing beds (3) which are found in the impure marbles of Central and South-East Asia, rich in clays and organic matter. These fluids were subsequently set in motion under the influence of tectonic pressures linked to the collision of continental plates.

Their interaction with the marbles caused chemical reactions which freed aluminium and chromophor elements of the ruby, like le chromium or vanadium. These elements, initially held in only trace quantities in these rocks, were shown to be mobile in sufficient quantity to produce ruby in this geological setting. Dissolution of salts from the evaporite beds led within the marble to the creation of cavities in which very pure rubies, with well developed faces, were able to develop. Contrary to what theoretical models elaborated up to now would suggest, the proposed model shows the involvement of salts and mineralizing fluids of metamorphic origin, the mineralization of the rubies taking place in the heart of the marble formations.

This model, which is new for natural ruby, proves to be close to the molten salts method used in industry for aluminium production.

The presence of evaporites is therefore a key element for explaining these ruby mineralizations. It is a sign for the carrying rock of a primary environment of a particular nature, the "lagoon" type where sedimentation took place in close relation with the ocean.

Their existence inside the marble formations is still, moreover, rare, which fits the very small number of deposits recorded and their small geographical spread. For the partner countries that are mining these deposits, this model brings information about the history, the structure and the geochemistry of these ruby formations, knowledge which is essential for conducting new prospecting campaigns in these regions of Asia.

Bénédicte ROBERT | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>