Diamonds in Tamil Nadu!!

Nature journal is skeptical about the report of microdiamonds from the Tamil Nadu coast, which was reported in Current Science. Read the Nature article.

Beach diamonds not for picking yet

All that glitters may not be diamond.All that glitters may not be diamond.

A recent report by geologists at Dr. H.S. Gour University at Sagar in Madhya Pradesh has raised a controversy: are the beaches of Tamilnadu in southeastern India really strewn with nuggets of diamond as these scientists claim?

A few days ago P. K. Kathal, his doctoral student M. K. Purohit and co-worker S. H. Adil announced that they have found 'micro-and macro-diamonds' in Nagapattinam and Vedaranyam beaches of Tamilnadu coast. These diamonds are so called because they are less than a millimeter in size. "A thorough search of the entire coast might yield larger diamonds," Kathal told Nature India and recommended detailed exploration of the entire Tamilnadu coast.

Their 'discovery' was reported in one of India's leading science journals1 with a photograph of the beach diamond on the cover page. That and a spate of media reports about the treasure on the sands may have already sent eager prospectors to the beaches with sieves in their hands.

But some geologists like Gopalakrishnarao Parthasarathy of the National Geophysical Research Institute in Hyderabad are skeptical about the find. "We have to make absolutely sure that what was discovered in the beaches is indeed diamond and not something else," he told Nature India.

Parthasarathy recalled that after the December 2004 Tsunami there were reports from the Geological Survey of India (GSI) of the occurrence of micro-diamonds in Kanyakumari beach. "It eventually proved to be zircon and not diamond," he said. "Zirconium silicate (or zircon) resembles diamond, and hence usually is mistaken for diamond."

Beaches usually are repositories of all products derived from the catchments of nearby rivers, coastal belt and continental region, including grains leaching from coastal rocks that contain heavy minerals like ilmenite, rutile, zircon, garnet, sillimanite and monazite.

In their study, the Sagar researchers collected sand samples from 16 beaches along the 2500-km coast from Puri to Kanyakumari. After filtration and wet-sieving to remove all the sand and heavy minerals, they hand-picked those grains showing brilliant luster.

According to the scientists, their study yielded 16 lustrous grains from Nagapattinam sample and 13 from Vedaranyam beaches.

"Normally, 6 grains of diamond per 100 grams of sediments is (considered a good) deposit," Purohit told Nature India. "In our case it is 13 to 16 grains, some of them bigger than one millimeter in size. This finding may lead to more (as well as) bigger diamonds in sediments in the area from Vedaranyam to Nagapattinam."
Map of Nagapattinam and Vedaranniyam beaches in the east coast of India from where the 'diamonds' were obtained.Map of Nagapattinam and Vedaranniyam beaches in the east coast of India from where the 'diamonds' were obtained.

"This is indeed a first report of micro- and macro-diamonds from the region with economic implications — a reason why the journal front-paged our paper," Purohit said.

But questions have been raised over the authenticity of the claims and also over the reported source of the beach diamonds.

According to the Sagar scientists, the beach grains were identified as micro- and macro-diamonds after visual examination using different types of microscopes. Kathal says examination a petrological microscope revealed their octahedron shape, brilliant (admandine) lustre, and 'isotropic' nature that are the very characteristic of diamonds. The morphological and optical characteristics of the beach grains combined with results of X-ray diffraction analysis confirm they are diamonds, Kathal said. "There should be no doubt on their identification."

However, according to Parthasarathy, an expert in characterization of minerals, while X-ray diffraction analysis is suitable for large crystalline diamonds, "laser Raman spectroscopy is the only method for unambiguous identification of micro-diamonds and practised by experimental scientists throughout the world."

From the size and shape of the recovered 'diamond' grains the scientists guess that they are released from a nearby kimberlite source. Kimberlites — 'plutonic' rocks that occur in the Earth's crust in vertical structures known as kimberlite pipes — are the most important source of mined diamonds today. According to Kathal an earlier study by the GSI in 2007 had indicated the presence of kimberlites in Mahboobnagar district of Andhra Pradesh suggesting that this may be the source of the bounty on Tamilnadu beaches.

"Nagapattinam and Vedaranyam fall in Godavari delta. Godavari has a very large basin," Kathal observed.

Parthasarathy, however points out the Mahboobnagar kimberlite is 'non-diamondiferous' and the only diamond bearing pipe is at Wajrakarur in Anathapur district of Andhra Pradesh. In any case, he says, there is no way these diamonds from Andhra Pradesh can be transported to Nagapattinam beach, by any normal geological or weathering processes. "To my knowledge there are no kimberlites in Tamilnadu or in Cauvery river zone" that could account for the presence of diamonds in the beach sands of Tamilnadu, he adds.
The 'diamonds' obtained from the beaches.The 'diamonds' obtained from the beaches.

Kathal says he never proclaimed that Mahboobnagar Kimberlite could have released the diamonds. "Our finding should rather be taken as an evidence of possible kimberlite pipe/pipes in the basin so that larger/more diamonds could be found in future," he said. The Sagar scientists, however, do not rule out the possibility that some of the recovered diamonds might have been introduced by extra-terrestrial objects like meteorites that fell on the Earth.

But S.V.S.Murty, chairman of the Planetary Sciences Division at Physical Research Laboratory (PRL) in Ahmedabad considers their extra-terrestrial nature highly unlikely.

"I am not commenting on the authenticity of identification of the grains as diamonds," he told Nature India. "I am only telling that (if they are indeed diamonds) they are certainly terrestrial in origin." The extra-terrestrial (meteoritic) diamonds, according to Murty, will be much smaller in size (nano-diamonds) than what the Sagar scientists claim to have discovered in the Tamilnadu beaches.

Parthasarathy suggests that the Sagar team "may have to contact some Raman spectrosocpist to confirm" that they have indeed discovered diamonds and also identify a more realistic origin of in the vicinity of where they were found.

Anxious prospectors should wait till then.

References
Purohit, M. K. et al. Discovery of micro-diamonds in beach sands of the Nagapattinam and Vedaranniyam beaches, southern east coast of India. Curr. Sci. 96, 767-768 (2009)

Reunion day

April 20th was some sort of red-letter day and Stephen was literal sporting and spouting red! Sahji, Sreenath, Riju and me came together after a really long period, we had been on our own ways and there was never much chance to meet, but with the magnetic Riju around there was no escaping. The ocassion also was a happy one for Dr Anirudhan who now heads the dept at Kariavattom for the next 3 years. Shaji is dabbling with Metamorphism as well as Hydrogeology these days, and his MSc students have started looking into the fluid processes in cordierite formation from the KKB. With a US govt GIS analyst in the form of Riju offering collaboration the dept's GIS endeavors are bound to get a boost, as also some international exposure.

Kerala: Natural Radiation - no risk?

Natural radiation poses no major risk

K. S. Jayaraman


Team leader Sher Ali.Genetic risk due to high natural background radiation is "a lot less than one has imagined earlier," according to a study just reported by researchers at the National Institute of Immunology NII in New Delhi1.

While natural background radiation may be responsible for varying alterations, it leaves the DNA of the vital germ line intact, they say. "Our study shows that the germ line is protected because the human genome has some unknown but powerful mechanism of protecting it," Sher Ali, a molecular geneticist who led the team told Nature India.

The findings should put at rest fears that people living in coastal areas of the south Indian state of Kerala are at risk of becoming infertile because they are exposed to natural background radiation that is ten-fold higher than the worldwide average. The radiation is the result of thorium bearing monazite minerals in the beach sands.

In their study the NII team looked for possible structural variations in the Y chromosome in blood and semen samples of 390 males of two generations at Chavara and Thevara — two high radiation regions of Kerala. They compared the results with those obtained from similar samples from 390 healthy unexposed males of matched age groups from Kochi (Kerala) and 400 normal males from different parts of India.

"We chose the Y chromosome as it is an ideal candidate to be assessed for possible genetic alterations induced by ionizing radiation due to its haploid status (having only one member of chromosome pair)," Ali said.

Containing fewer than 50 genes or gene families coding for proteins, Y-chromosome is not essential for life but harbors several testis-specific genes necessary for sperm production, and hence continuation of the species. At least three non-overlapping regions of the Y chromosome — (Azoospermia factors a, b, and c) — are essential for sperm production. Micro-deletions in these regions affecting one or more of the candidate genes (DAZ, RBMY, DBY, and USP9Y) cause male infertility. The SRY gene in the Y chromosome plays a predominant role in male sex determination.

The scientists found that barring two per cent, all the 790 unexposed (control) males from Kerala and other parts of India were free from micro-deletions. In contrast more than 90 per cent of males exposed to background radiation showed random micro-deletions in the Azoospermia factor. And, in about 80 per cent of them tandem duplication and multiple copies of 11 different Y-linked genes were found. For instance, more than 85 per cent of exposed males showed 2-8 copies of the SRY gene.

But remarkably all these genetic alterations in the exposed population were detected only in blood samples but not in the germ line (sperm) samples suggesting that sperm cells are somehow protected from background radiation. "Absence of micro-deletions in the germline explains the normal fertility status of the exposed males," Sanjay Premi, one of the authors told Nature India.

Where do the germ cells derive the protection from? Ali says that germ cells, originating from the gonad's somatic cells, most likely activate some still unknown genes that sense the defective ones and triggers apoptosis (programmed cell death). "The defective sperms are eliminated and quickly replaced by fresh ones and thus what we see is always a clean picture in case of germ line," Ali said. However that is not true in case of blood cells meaning blood cells are not treated in the same way as germ cells in the body. "I would love to call it nature's marvel," Ali said adding that "this is the hypothesis; we are yet to prove this."

According to the NII scientists the tandem duplication and multiple copies of genes detected in blood samples of exposed population "is a possible genome strategy to absorb the mutational loads caused by the radiation."

Previous studies on the high radiation areas of Kerala were focused on the cases of Down's syndrome, congenital malformations, chromosomal aberrations in humans and phenotypic changes in the rats. Some groups also focused on the frequencies of the repeated abortions in human females. "In other parts of world, people have studied rates of minisattellite mutations, mitochondrial mutations in the populations exposed to radiations due to industrial accidents or nuclear bombings," said Premi. "On the contrary, we have analysed the single chromosome Y in a much greater detail both at somatic and germ line levels. To our information no one in the world has analysed germ line and somatic cells in the manner we have done."

Premi said that on the basis of the study it has been concluded that the study populations have adapted themselves to the high background radiation. "The (genetic) alterations we recorded were random and did not represent any major Y chromosome-related recombination losses or duplications reported in the literature which has been held responsible for the infertility."

References
Premi, S. et al. Unique signatures of natural background radiation on human Y chromosomes from Kerala, India. [journal]PLoS ONE[/journal] 4, e4541. 2009)