ΔΙΕΘΝΕΣΔΙΕΘΝΕΣχρυσόςπανάλαφρος

Ο πανάλαφρος χρυσός των 20 καρατίων που κατά 98% είναι αέρας και επιπλέει στο νερό

Ο πανάλαφρος χρυσός των 20 καρατίων που κατά 98% είναι αέρας και επιπλέει στο νερό
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Replica of a large fluvial gold nugget (placer gold) ("Oregon Canyon Nugget") from California. (SDSMT 1473, South Dakota School of Mines and Technology Museum of Geology, Rapid City, South Dakota, USA)A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals. To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals.Gold (Au) is the most prestigious metal known, but it's not the most valuable. Gold is the only metal that has a deep, rich, metallic yellow color. Almost all other metals are silvery-colored. Gold is very rare in crustal rocks - it averages about 5 ppb (parts per billion). Where gold has been concentrated, it occurs as wires, dendritic crystals, twisted sheets, octahedral crystals, and variably-shaped nuggets. It most commonly occurs in hydrothermal quartz veins, disseminated in some contact- & hydrothermal-metamorphic rocks, and in placer deposits. Placers are concentrations of heavy minerals in stream gravels or in cracks on bedrock-floored streams. Gold has a high specific gravity (about 19), so it easily accumulates in placer deposits. Its high density allows prospectors to readily collect placer gold by panning. In addition to its high density, gold has a high melting point (over 1000º C). Gold is also relatively soft - about 2.5 to 3 on the Mohs Hardness Scale. The use of pure gold or high-purity gold in jewelry is not desirable as it easily gets scratched. The addition of other metals to gold to increase the hardness also alters the unique color of gold. Gold jewelry made & sold in America doesnât have the gorgeous rich color of high-purity gold.The specimen shown above is a replica of a large gold nugget.Locality: El Dorado County, California, USA
Replica of a large fluvial gold nugget (placer gold) ("Oregon Canyon Nugget") from California. (SDSMT 1473, South Dakota School of Mines and Technology Museum of Geology, Rapid City, South Dakota, USA)A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals. To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals.Gold (Au) is the most prestigious metal known, but it's not the most valuable. Gold is the only metal that has a deep, rich, metallic yellow color. Almost all other metals are silvery-colored. Gold is very rare in crustal rocks - it averages about 5 ppb (parts per billion). Where gold has been concentrated, it occurs as wires, dendritic crystals, twisted sheets, octahedral crystals, and variably-shaped nuggets. It most commonly occurs in hydrothermal quartz veins, disseminated in some contact- & hydrothermal-metamorphic rocks, and in placer deposits. Placers are concentrations of heavy minerals in stream gravels or in cracks on bedrock-floored streams. Gold has a high specific gravity (about 19), so it easily accumulates in placer deposits. Its high density allows prospectors to readily collect placer gold by panning. In addition to its high density, gold has a high melting point (over 1000º C). Gold is also relatively soft - about 2.5 to 3 on the Mohs Hardness Scale. The use of pure gold or high-purity gold in jewelry is not desirable as it easily gets scratched. The addition of other metals to gold to increase the hardness also alters the unique color of gold. Gold jewelry made & sold in America doesnât have the gorgeous rich color of high-purity gold.The specimen shown above is a replica of a large gold nugget.Locality: El Dorado County, California, USA
James St. John/Flickr

Επιστήμονες στην Ελβετία δημιούργησαν χρυσό ελαφρύ σαν αφρό, που επιπλέει στο νερό. Αν και είναι περίπου 20 καρατίων, το 98% είναι αέρας και μπορεί άνετα να επιπλέει στο αφρόγαλα ενός καπουτσίνο! Πρόκειται για την ελαφρύτερη μορφή οποιουδήποτε πολυτίμου μετάλλου έχει ποτέ παραχθεί μέχρι σήμερα.

Ο χρυσός-αφρός είναι χίλιες φορές πιο ελαφρύς από τον κανονικό χρυσό, παρόλα αυτά είναι σχεδόν αδύνατο να καταλάβει κανείς τη διαφορά με γυμνό μάτι, καθώς έχει το χαρακτηριστικό χρώμα και τη γνωστή μεταλλική λάμψη του χρυσού. Αν τον πιάσει όμως κανείς, είναι πιο μαλακός και εύπλαστος.

Οι ερευνητές του Ελβετικού Ομοσπονδιακού Ινστιτούτου Τεχνολογίας (ΕΤΗ) στη Ζυρίχη, με επικεφαλής τον καθηγητή Ραφαέλε Μετσένγκα, έκαναν τη σχετική δημοσίευση στο περιοδικό για νέα υλικά «Advanced Materials».

Το νέο πορώδες υλικό αποτελείται από 98 μέρη αέρα και δύο μέρη στερεού υλικού. Από αυτό το στερεό υλικό, τα τέσσερα πέμπτα είναι καθαρός χρυσός και το υπόλοιπο ένα πέμπτο είναι πρωτεΐνη γάλακτος.

Το ασυνήθιστο υλικό αποτελεί μια μορφή αερογέλης, ελαφρύτερη από το νερό και σχεδόν τόσο ελαφριά όσο ο αέρας. Η διαφορά μιας υδρογέλης από μια αερογέλη (ή αεροπήκτωμα) είναι ότι το υγρό της πρώτης αντικαθίσταται από αέρα, ενώ διατηρείται η δομή του υλικού.

Οι ερευνητές αρχικά θέρμαναν πρωτεΐνες γάλακτος για να παράγουν ίνες πάχους μερικών νανομέτρων, τις οποίες μετά τοποθέτησαν σε ένα διάλυμα με άλας χρυσού. Οι ίνες δημιούργησαν ένα πλέγμα, πάνω στο οποίο συγκεντρώθηκαν κρύσταλλοι (νανοσωματίδια) χρυσού, με τελικό αποτέλεσμα μια χρυσή αερογέλη.

Οι ερευνητές δήλωσαν ότι ο πανάλαφρος χρυσός θα μπορούσε να βρει πρακτικές εφαρμογές εκεί όπου χρησιμοποιείται ήδη ο κανονικός χρυσός, ακόμη και για την κατασκευή χρυσών ρολογιών και κοσμημάτων. 'Άλλες πιθανές εφαρμογές είναι η χρήση του ως καταλύτη σε χημικές αντιδράσεις, στην παραγωγή ηλεκτρικών αισθητήρων πίεσης κ.α.

(Με πληροφορίες από ΑΠΕ - ΜΠΕ)

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