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Gold Prospecting
Metal Detecting for Gold
First interesting finds! and Question re identification
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<blockquote data-quote="XLOOX" data-source="post: 591355" data-attributes="member: 16174"><p>I have always struggled with getting much useful info from density since when faced with a heavyish-for-size lump of grey metal my question is mainly is it silver or is it lead. </p><p></p><p>SG of Pb=11.4 & Ag=10.5 so a 5g nugget of lead has a volume of 0.44ml & silver 0.48ml. Even a 30g nugget is 2.68ml vs 2.86ml</p><p></p><p>Good luck measuring to 0.04ml or even 0.18ml precision on a measuring cylider with a diameter big enough to take your nugget & even if you get a result you believe to be an accurate SG then so what? - with the strong likelihood that the silver or lead is alloyed the SG you get is not that helpful in differentiating the two metals. </p><p></p><p>Add in the impact of crevices holding micro air bubbles & dirt or meniscus & wetting issues if using mass of overflow methods & it is not generally not worth the effort in measuring SG on small lumps unless you suspect Pt (SG 21.5) & even then with a 5g nugget it only 0.21ml difference.</p><p></p><p>Hardness is a very strong indicator & melting point is a clincher as all Pb/Sn/Sb/Bi alloys will have MUCH lower melting points than any grey Cu/Ag/Au alloy (which would have to be at least 70% Ag to be grey).</p></blockquote><p></p>
[QUOTE="XLOOX, post: 591355, member: 16174"] I have always struggled with getting much useful info from density since when faced with a heavyish-for-size lump of grey metal my question is mainly is it silver or is it lead. SG of Pb=11.4 & Ag=10.5 so a 5g nugget of lead has a volume of 0.44ml & silver 0.48ml. Even a 30g nugget is 2.68ml vs 2.86ml Good luck measuring to 0.04ml or even 0.18ml precision on a measuring cylider with a diameter big enough to take your nugget & even if you get a result you believe to be an accurate SG then so what? - with the strong likelihood that the silver or lead is alloyed the SG you get is not that helpful in differentiating the two metals. Add in the impact of crevices holding micro air bubbles & dirt or meniscus & wetting issues if using mass of overflow methods & it is not generally not worth the effort in measuring SG on small lumps unless you suspect Pt (SG 21.5) & even then with a 5g nugget it only 0.21ml difference. Hardness is a very strong indicator & melting point is a clincher as all Pb/Sn/Sb/Bi alloys will have MUCH lower melting points than any grey Cu/Ag/Au alloy (which would have to be at least 70% Ag to be grey). [/QUOTE]
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Gold Prospecting
Metal Detecting for Gold
First interesting finds! and Question re identification
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