Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Asian rubies come always with marble and salt

30.01.2004


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.

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 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

Marie Guillaume | alfa
Further information:
http://www.ird.fr/us/actualites/fiches/2003/index.htm

More articles from Earth Sciences:

nachricht Climate Change in West Africa
17.06.2019 | Julius-Maximilians-Universität Würzburg

nachricht Determining the Earth’s gravity field more accurately than ever before
13.06.2019 | Technische Universität Graz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

A new force for optical tweezers awakens

19.06.2019 | Physics and Astronomy

New AI system manages road infrastructure via Google Street View

19.06.2019 | Information Technology

A new manufacturing process for aluminum alloys

19.06.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>