Rarest Gemstones: Jeremejevite

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Jeremejevite, one of the rarest gemological materials, was named after Russian mineralogist P. W. Jeremejev in 1883, but there are rarely any specimens found in Russia today. Recently Namibia has started to produce some mentionable crystals, but in such small amounts the stone is still very rare. Jeremejevite is typically found in pale blue-green, cornflower-blue to yellowish bown hues.

JEREMEJEVITE CLASSIFICATION
Common Name: Jeremejevite
Species: Jeremejevite
Colors: blue-green, cornflower blue, brown, pale yellow and colorless

Key Separations: RI, birefringence and possible optic character.

JEREMEJEVITE PROPERTIES
Chemical Name: aluminum borate fluoride hydroxide
Chemical Formula: Al6B5O15(F,OH)3
Crystal System: Hexagonal
Classification: Borate
Crystallinity: Crystalline
Transparency: Transparent
Refractive Index: 1.64-1.651 Tolerance: (+0.002/-0.001)
Birefringence: 0.009
Optic Character: uniaxial and biaxial
Optic Sign: negative
Polariscope Reaction: doubly refractive (DR)
Fluorescence: SWUV: Inert, LWUV: Inert
Hardness: 6.5-7.5
Streak: white
Specific Gravity: 3.27-3.31
Toughness: Poor
Luster: Vitreous
Fracture: Conchoidal
Cleavage: None

Jeremejevite was first described in 1883 by French mineralogist Augustin Alexis Damour, who named it in honour of the Russian mineralogist and engineer Pavel Wladimirowich Jeremejev. Only a few localities of this rare borate mineral are known worldwide. Jeremejevite was discovered in 1883 at Mt Soktuj, Eastern Siberia, Russia. Only a few isolated crystals up to 5 cm in length have been reported from the type locality. The crystals resembled a yellowish beryl in appearance. For more than 100 years, this mineral was one of the rarest of all known minerals.

In 1973 a second occurrence of jeremejevite was found at a small pegmatite mine known as “Mile 72” north of Swakopmund, Namibia. The mine was exploited by the well-known mineral dealer Sid Pieters. Only a few crystals were found, which showed a fine blue colour. In 1976 a pocket was hit that produced about 100 of the finest known crystals of blue jeremejevite measuring up to 5 cm in length and 0,5 cm in diameter. Very few crystals on matrix were found.

Since this find, jeremejevite became a highly sought-after mineral by collectors worldwide. The only other known localities are the Ameib Farm Erongo Mountains, Namibia; Eifel Mountains, Germany; Sagaing District, Burma (Myanmar); and the Pamir Mountains, Tajikistan. The latter find is not well documented. About 10 yellow to brown crystals of little transparency up to 5 cm in length are reported from this locality.

The Mile 72 Namibian occurrence is in a wind-blown flat surface of hard, ocean-weathered granite protruding from a sandy stretch of beach about 750 m back from the shoreline, where the breakers lap the Namib Desert. It is close to milepost 72; that is, 72 miles by road north of Swakopmund.

The initial discovery was made by a woman known as “Tannie Klippie”, who was the wife of John Marais. Mr Marais was employed by the state as a road-grader operator, and his wife frequently spent her days walking behind her husband’s grader collecting pretty rocks. In 1973 the road leading to the Mile 72 fishing camp road was angled at approximately 45 degrees southward to the coast road from its current location. Mr Marais’ grader turned over a few jeremejevite crystals that had weathered out into the sand, and Tannie Klippie was there to pick them up. These specimens eventually made their way to the sharp eye of Windhoek gem and mineral dealer Sid Pieters. At first glance Pieters thought them to be aquamarine but an analysis identified them as jeremejevite. This was confirmed by an analysis of a cut gem performed by Richard T. Liddicoat of the Gemological Institute of America (1973) .

Mr Pieters quickly filed three 300 x 600 m claims where Tannie Klippie stumbled over the crystals. Peter Kitler did the actual mining and the tourmaline miner, Jan Coetzee, from Usakos did the blasting. They decided to open cut the granite, beginning on the eastern end and drive a trench westward perpendicular to the vertical vein containing the jeremejevite pockets. The first pocket found was in the altered granite. It yielded a number of gemmy but colourless crystals to 7,6 cm. The trench was continued through 5-6 m of hard granite, maintaining a depth of 1,5 m. This work netted just a meagre handful of loose, colourless crystals from small pockets along the vein.

In mid-1998, Brian Lees of Collector’s Edge Minerals teamed up with C. J. Johnston, an American mining geologist and mineral dealer based in Omaruru, to form Khan River Mining (Pty) Ltd. Their intention was to excavate further along the pegmatite veins in the hope of finding more jeremejevite. The mining commenced in early January 1999 and upon cleaning out the “Kitler pit” the first truly mechanized mining effort at Mile 72 commenced. In spite of a difficult mining environment 2 700 tons of rock were removed within the first six months. With the advantage of having heavy equipment more rock was mined in the first two weeks than the entire Sid Pieters effort from 1973 to 1976. Within the first three weeks, directly below the area where the best material had been found in 1973, a coarse-grained granitic pegmatite was encountered which produced approximately 300 single, colourless to pale yellow water-clear jeremejevite crystals up to 5 cm and only one pale blue crystal. Over the next 12 months an additional 14 target areas were identified and an estimated 2 300 tons of rock mined. In addition to these targets 15 trenches were excavated. While the effort produced some interesting specimens of feldspar, apatite, quartz and schorl, no further jeremejevites were found. Namibia is one of the very few countries in the world that constitutionally guarantees the protection of the environment. Consequently it is highly unlikely that any further mining will take place at Mile 72.

In March 2001, pegmatites containing jeremejevite were discovered near the summit of an isolated inselberg on Farm Ameib near the border with the farm Davib-ost, halfway between the village of Tubussis and the town of Usakos on the south side of the Erongo Mountains. As with the Mile 72 crystals, the first intense blue crystals found were thought to be aquamarines, and caused little excitement. A few thousand crystals have since been recovered. These workings are restricted to a 100 m2 area on a steeply sloping surface near the top of the inselberg. The mining in the Erongo Mountains is a simple brute force manual labour affair. The diggers must first walk 14 kilometres from the Government gravel road to reach the base of the mountain. It is then a very hard climb of nearly 500m to reach the top. There is no water, so miners must carry their own supply together with their modest equipment. The majority of the diggers, who have numbered up to 150, have nothing more than a hammer, chisel and shovel with which to attack the granite. Some of the excavations now exceed 6 m in depth. The majority of the Erongo Mountain jeremejevite crystals are under 2,5 cm in size, but a respectable number of larger crystals, over 200, range up to 5 cm in length and 1 cm wide. There have been unverified reports of crystals in excess of 8 cm.

You might also read this article by Kenneth Scarratt, Donna Beaton and Garry Du Toit on Gems&Gemology

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Industry Analysis: Holiday Sales Off to a Strong Start

We publish courtesy of Gems & Gemology GIA Insider

Author: Russell Shor, Senior Industry Analyst

 

This 27.19 ct D-IF dimaond sold for $3.66 million at Sotheby's Dec. 9 Magnificent Jewels auction in New York. Photo courtesy Sotheby's.

 

 

 

This GIA-graded Fancy Intense pink diamond brokle two records: the most ever paid for a gemstone at auction and the highest price per carat ($1.86 million). Photo courtesy Sotheby's

 

 

 

 

The biggest development of this final month of 2010 is the spate of good news. Top jewelry auctions continue to break price records around the world, while the U.S. holiday shopping season indicates that jewelry is high on the buying list for everyday consumers.
One retail analyst group, IBIS World Inc., estimates that jewelry demand will rise 6% over the 2009 season. Earlier in the year, analysts were forecasting increases of around 2-3%, based largely on predictions of increased spending among the wealthiest buyers. Retail jewelers report, however, that sales have risen higher than expected across the board since mid-November.
Press reports and anecdotal evidence indicate that both the volume of sales and the average ticket price will be up significantly over the same period last year, even adjusting for gold price inflation, as consumers feel more comfortable spending. The Centurion newsletter survey reported that some 60% of luxury jewelers have posted double-digit sales increases thus far, while an additional 14.8% were up between 6% and 10%. Tiffany & Co. and Blue Nile have had seasonal gains of 10% and 12%, respectively.
Independent retailers are also optimistic about the season. Traditionally, as much as one-third of their holiday sales take place during the final 10 days before Christmas.
One reason for the better-than-expected retail sales is that most economists are no longer warning about a “double dip” recession. The consensus is that while a struggling job market will remain a drag on recovery, the economy will continue a slow growth through 2011. In addition, U.S. corporate profits have been quite strong the past two quarters, which suggests that those who have jobs may no longer fear losing them or being subjected to cuts in wages and hours.
In Europe, the fiscal troubles of Ireland and possibly Spain have unsettled the European Union. But while the European recovery remains slower, there is no talk of these problems pushing the world back into recession, as was the case last summer when Greece’s problems came to light.
The ultra-wealthy continue to flock to very large colorless and top fancy-color diamonds and extremely fine-colored stones. The Nov. 16 Sotheby’s auction in Geneva was a record-breaker on a number of fronts. It was the first $100 million-plus jewelry auction ever. Nearly half of that total, $46.1 million, went to a 24.78 ct GIA-graded Fancy Intense pink diamond that broke two records: the most ever paid for a gemstone at auction and the highest price per carat ($1.86 million).
The following day, at Christie’s Geneva, two Colombian emeralds sold for extremely high prices: A 25.83 ct octagon-shaped stone went for $1.04 million, while a 9.27 ct Muzo stone drew a winning bid of $824,720.
Sotheby’s Dec. 9 Magnificent Jewels auction in New York broke a sales record for that venue: $53.2 million, with 10 lots selling for more than $1 million. The top lot was a 27.19 ct D-IF diamond that sold for $3.66 million, or nearly $135,000 per carat.
Meanwhile, preliminary reports from the Dec. 13-17 Diamond Trading Company sight put it at about $450-$475 million. Diamond manufacturers hope the encouraging U.S. holiday season, coupled with continued strong demand from India and China, will break the impasse over polished prices that has lasted for six months.
Rough prices have increased far ahead of polished, as cautious retailers and jewelry manufacturers still refuse to pay higher rates. A number of manufacturers, particularly in India, stopped polishing certain sizes, preferring to hold them until prices improve, instead selling from inventory or stones sourced from the secondary market.
Russell Shor
Senior Industry Analyst

 

 

GIA Lab Grades Largest (4+ ct) HPHT-Grown Synthetic Diamond Submitted to Date

We publish courtesy of Gems & Gemology eBrief

Authors: Wuyi Wang and Tom Moses


Synthetic diamonds have improved dramatically in recent years. The GIA Laboratory recently examined the largest faceted synthetic diamond ever submitted for testing and grading: a rectangular sample measuring 9.07 x 8.54 x 5.98 mm and weighing 4.09 ct. It was color graded Fancy Vivid yellow-orange and had notably even color distribution (color zoning is common in HPHT-grown synthetic diamonds). Some strings of black pinpoint inclusions were seen with the microscope; the clarity grade was VS1. DiamondView imaging showed typical HPHT synthetic growth sectors, with patterns of varying intensity and color.

The mid-IR absorption spectrum revealed a high concentration of predominantly A-form nitrogen, as well as isolated nitrogen (weak absorption at 1344 cm-1) — which was responsible for the yellow-orange color. The UV-Vis absorption spectrum showed a typical pattern for isolated nitrogen (gradual increase in absorption from approximately 570 nm to higher energies), as well as features attributed to a Ni-related defect (793.6 nm) and the H2 defect (986.2 nm).

The predominantly A-form nitrogen and the occurrence of the H2 optical center strongly suggest growth at a relatively high temperature. An advantage to high-temperature synthesis is that it limits the development of growth sectors other than octahedra. As a result, the color appears more evenly distributed.

This sample’s size, clarity, and vivid, evenly distributed yellow-orange color were exceptional and demonstrate continued improvements in the HPHT growth technique.

Wuyi Wang and Tom Moses
GIA Laboratory, New York

Recent Finds of Aquamarine and Heliodor in Indochina

We publish courtesy of Gems & Gemology eBrief

Author: Brendan Laurs

 

In June 2010, GIA was informed by Jack Lowell (Colorado Gem & Mineral Co., Tempe, Arizona) about some attractive gem-quality crystals of aquamarine and heliodor from Indochina. According to his supplier (Tan Pham, Vietrocks.com, Philadelphia), good-quality aquamarine was mined in 2008 in northern Vietnam, from separate areas in the neighboring provinces of Thanh Hoa (in Thuong Xuan District) and Nghe An (Que Phong District). Aquamarine from Nghe An was also produced in 2003-2004. The more recent crystals range up to 20 cm long, and are notable for their saturated color. Matrix specimens (associated with smoky quartz) have been recovered only rarely, from Thanh Hoa, due to the weathered nature of the pegmatite host rocks. Clean gemstones up to approximately 35 ct have been faceted from the Vietnamese aquamarine.

Well-formed crystals of heliodor (e.g., figure 2) were recently produced from another area in Southeast Asia, which Mr. Pham suspects is Cambodia. The crystals were first noted on the market in Vietnam with a third-party source in 2007; those seen by Mr. Pham ranged up to 7.5 cm long. This heliodor, as well as the aquamarine described above, has been especially popular with Chinese buyers.

Brendan M. Laurs


New Field Research Confirms Tibetan Andesine

We publish courtesy of Gems & Gemology eBrief

Authors: Ahmadjan AbduriyimBrendan M. Laurs

An international group traveled to Tibet in late September 2010 to investigate the controversial origin of red andesine from China. The group was organized by coauthor AA and hosted by miner Li Tong and his wife Lou Li Ping. It also included Richard Hughes (Sino Resources Mining Corp., Hong Kong), Flavie Isatelle (geologist, France), Christina Iu (M.P. Gem Corp., Kofu, Japan), Thanong Leelawatanasuk (GIT, Bangkok), Young Sze Man (Jewellery News Asia, Hong Kong), and coauthor BML. Our goal was to examine three reported Tibetan andesine localities located close to one another 90 minutes southeast of Shigatse: Bainang, Zha Lin, and Yu Lin Gu.
AA visited the Bainang mine, reportedly Tibet’s principal source of andesine, in 2008. Most of the mining there took place in 2005-2008 and was organized by Li Tong. Unfortunately, despite having official permission from the Chinese government and police escorts, a powerful local lama would not allow us to visit the deposit.

Local people using simple hand tools mined the Zha Lin deposit in 2006-2008, reportedly producing approximately 2 tonnes of andesine. We saw a series of shallow pits within the medium-gray silty soil that underlies alluvium consisting mainly of shale and mudstone. We recovered andesine from two small pits (120 cm maximum depth) we dug in the mine area, and from two out of three pits dug in random areas of undisturbed alluvium 30-50 m upslope from the mining area. As seen previously in Tibetan andesine, all the rough material was rounded and ranged from pale to deep red with a few pieces containing bluish green areas.

The Yu Lin Gu occurrence is hosted by an alluvial fan located approximately 2 km up-valley from Zha Lin. Nearly 200 kg of andesine has reportedly been picked up from the surface by locals since 2006. We recovered andesine from the surface or slightly below the surface in loose silty soil, but did not find any stones when we dug pits into the alluvial fan. The range of color and degree of rounding of these pieces were similar to those from Zha Lin, but many had less-saturated coloration.

We were unable to verify whether Yu Lin Gu is a true andesine deposit because we could not find samples at depth. Our discovery of andesine within pits dug in random, previously unexplored areas near the Zha Lin mine, however, provided proof of a genuine Tibetan andesine deposit. The original source rock for the andesine was not evident in the area, and may have previously eroded away.

Ahmadjan Abduriyim
Gemmological Association of All Japan – Zenhokyo, Tokyo

Brendan M. Laurs

Editor, Gems & Gemology, GIA Carlsbad
Note: This report may be downloaded in PDF form here

Industry Analysis: Rough Market Stays Hot, Polished Diamonds Lukewarm

We publish courtesy of Gems & Gemology’s G&G GIA Insider

Author: Russell Shor, Senior Industry Analyst

The rough diamond market continues to run much hotter than the polished market. The Diamond Trading Company’s Oct. 4-8 sight, initially estimated at $425 million, increased to nearly $500 million as clients requested additional allocations.
The DTC held the line on prices, but rough sold at tender auctions from other producers and the DTC subsidiary Diamdel was reportedly up 10% or more from the previous month.
Alrosa, the world’s second-largest producer, announced rough sales of $2.53 billion for the first nine months of the year, an increase of nearly 50% over 2008 (the last “normal” year). However, price increases accounted for more than half that figure. The company expects its 2010 rough sales to total $3.3 billion (compared to DTC’s estimated $5.8 billion). Alrosa’s production was mined in Russia, except for about $450 million worth from Angola’s Catoca mine.
At odds with the continued high demand for rough is a very cautious polished market worldwide. As noted in last month’s Insider, buyers at the Hong Kong show were walking away from high polished prices that attempted to recoup up to half the rough increases. In the U.S., retailers are downgrading qualities and sizes to keep costs down.
U.S. retail jewelry sales have been running an estimated 3% ahead of 2009 levels, less than the 4% to 5% forecasted earlier this year.
Deloitte and the International Council of Shopping Centers predict that holiday retail sales overall will hover around 2% to 3% over last year, with jewelry falling within that range.
ZIMBABWE: Kimberley Process delegates will meet next month to determine whether to certify exports of rough diamonds from Zimbabwe’s Marange deposit. Zimbabwe’s government recently auctioned 1.3 million carats under KP supervision. The prices realized, coupled with reports from the area, indicate that the proportion of gem-quality diamonds is more than double the initial KP estimate of 5%. And the amount of near-gem material (destined for India) is reportedly 35%, which rivals Argyle. This means that as much as half the Marange production could be cuttable.
The huge size of the deposit, spread over hundreds of square miles, makes it difficult to properly survey — one reason Marange took the diamond world by surprise. Some estimates claim it could produce 40 million carats annually, which would make it the world’s most productive diamond area.
Ongoing concern over Zimbabwe’s human rights record and the fact the KP approved the rough diamond exports despite a U.S. ban on trade with that nation, is prompting talk of a two-tiered Kimberley Process system.
Proponents of this plan, which the U.S. State Department will reportedly promote at the November KP meeting, say the current system is too narrowly focused on “conflict” diamonds — diamonds sold by rebel groups to fund wars — and does not take into account human rights abuses by recognized governments of producing nations (i.e., Zimbabwe). They are also frustrated with the KP requirement of a unanimous vote by its members before it can initiate any action.
Opponents argue that a two-tiered KP system would create a “favored” diamond track for large producers such as De Beers and Rio Tinto and for branded Canadian diamonds, while casting unwarranted suspicion on diamonds from smaller producers.
MACRO: Spending Pulse noted that through the first nine months of 2010, online retail sales for all merchandise categories posted a 7.8% year-over-year growth. Online jewelry sales for September, however, fell 5.9% against the previous year. The luxury market research group also noted that September was the only month this year to record negative growth for the online jewelry category. Blue Nile, the largest online jewelry seller, reported a year-on-year sales increase of 9.7% for the second quarter (ending July 4) but has noted slower third-quarter sales (not yet announced).
The world’s two fastest-growing economies, China and India, are also increasingly important diamond markets. Both are on target for economic growth of about 10% this year, according to an International Monetary Fund (IMF) report.
The IMF’s latest World Economic Report says the Chinese economy will grow 10.5% in 2010 and 9.6% in 2011, driven by domestic demand. India’s gross domestic product will expand 9.7% in 2010 and 8.4% in 2011, as a result of strong industrial production.

The IMF noted that mature Western economies, continuing their slow recovery from the economic downturn, are forecast to grow 2.7% this year and 2.2% in 2011.

Intense Purplish Pink Synthetic Diamond, HPHT Grown and Treated

We publish courtesy of GIA’s Gems & Gemology G&G eBrief

Author: Paul Johnson, GIA Laboratory, New York

This 0.20 ct Fancy Intense purplish pink round brilliant proved to be a treated synthetic diamond. Photo by Jian Xin (Jae) Liao.

Many pink-to-red diamonds in the jewelry market owe their color to the natural material being treated with multiple processes, such as high-pressure, high-temperature (HPHT) annealing combined with irradiation and annealing at relatively low temperatures. This technique has also been applied to HPHT-grown synthetic diamonds since the 1990s, and today it appears that some of these synthetics are intentionally produced with very low nitrogen concentrations for a more intense color appearance after post-growth treatment.

A 0.20 ct round brilliant submitted to the New York laboratory was Fancy Intense purplish pink and contained few inclusions. Our initial observations suggested it might be one of the multiple-treated natural diamonds described above. It displayed strong color zoning and fluoresced strong orangy red to both long- and short-wave UV radiation. Absorption spectroscopy showed it was type Ia with very low nitrogen; the pink color was produced by strong NV centers with zero-phonon-line absorptions at 575 and 637 nm. These centers can be produced by multiple treatments, and an additional strong peak at 595 nm was indicative of artificial irradiation. These features are very similar to those seen in multiple-treated natural diamonds.
Careful examination with the DTC DiamondView instrument, however, revealed a subtle multi-sectoral growth structure that proved it was an HPHT-grown synthetic diamond. It appears that this synthetic diamond was carefully grown with a very low concentration of nitrogen (approximately 1 ppma), but enough to induce the high concentration of NV centers responsible for the intense pink color during post-growth treatment.

Care is needed to separate these treated synthetic pink-to-red diamonds from treated natural diamonds.