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joi, 22 decembrie 2016

O nouă monedă comemorativă din Insulele Cook - 21.12.2016

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Obverse and reverse of Cook Islands’ unusual Tamdakht meteorite commemorative silver $2. (Images courtesy Coin Invest Trust)

On Dec. 20, 2008, a stony meteorite fell in Morocco near the village of Tamdakht. Fragments were scattered over an oval area of 25 kilometers by 2 kilometers in the foothills of the High Atlas Mountains. The two largest formed small impact craters: one about a meter across and 70 centimeters deep, the other about 20 cm across and 20 cm deep.

The fall and its craters have been commemorated by a spectacular and innovative silver $2 struck for the Cook Islands by Liechtenstein’s Coin Invest Trust. The reverse design shows a concave impact crater about which the resulting debris is scattered in a radial pattern.

The coin’s crater was produced by first striking the 38.61 mm, half ounce .999 fine silver flan in the usual manner. The reverse was then intentionally overstruck to produce a series of cracks in the flan and also produced a breakthrough in the center of the crater such that the meteorite has seemingly struck the coin.

To emphasize the point a fragment of the actual meteorite is attached to the flan alongside this central hole. Even the lid of the transparent capsule housing the finished coin has been pierced by impact immediately above the crater center.

Each flan has responded differently to the violence of the destructive overstrike. As a consequence each coin is unique.

The fall was spectacular. An intensive long lasting fireball lit up the sky across sparsely populated regions of southwestern and central Morocco. It descended in an almost horizontal trajectory moving from the west coast towards the High Atlas.

It appeared to hit a mountain but this proved an illusion. It was travelling sufficiently low at the time that when it passed through a gap in the mountain range it vanished from sight.

Subsequently the resulting impact was heard over a wide area. It was preceded by explosions as the body broke up low in the atmosphere.

Several professional Moroccan meteorite prospectors launched an immediate search. The terrain is both remote and very broken. No vehicle access was possible and the area needed to be explored on foot. It took two weeks before the first fragments were found.

The Tamdakht meteorite, as it is now known, proved to be regular stony meteorite known to meteorite scientists as a chondrite. To date some 200 kiligrams of pieces have been recovered the largest of which exceeds 10 kg. One larger mass hit a limestone outcrop and shattered into many hundreds of smaller pieces.

The fascinating coin is produced with an antique finish and has a mintage of 2,500.

It is presently available from the Melbourne Mint. The website is www.melbournemintcoins.com.au. Email info@MelbourneMintCoins.com.au




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