Sunday, June 10, 2018

SpGr to estimate the gold content of electrum

Brutium Punic 3/8th Shekel
216 – 211 BC




I made some home SpGr estimates and conclude my coin is probably electrum! The % gold was taken from a conversion table in Jenkins & Lewis, Carthaginian Gold and Electrum Coins, pg 63. I made 5 series of weight measurements. First I measured the coin dry. Next I used Teflon dental floss to tie the coin on a string. I filled a small cup with water, placed the cup on my scale and zeroed the scale. I then held the coin in the cup, under water, without letting it touch the sides. To “confirm” my test, I tested one buffalo nickel, two Roman Republican denarii and one silver nugget.

SpGr = Wt of coin in air / Wt of coin in water




My results:


Coin
SpGr
% Gold
Wt, air
Wt, water
Bruttium Punic 3/8th shekel, test 1
11.95
27.0
2.51
0.210
Bruttium Punic 3/8th shekel, test 2
11.41
17.2
2.51
0.220
Bruttium Punic 3/8th shekel, test 3
10.96
9.0
2.52
0.230
Bruttium Punic 3/8th shekel, test 4
11.38
16.6
2.56
0.225
Bruttium Punic 3/8th shekel, test 5
12.05
28.5
2.53
0.210
Buffalo Nickel
8.68
4.86
0.560
Denarius, MN.CORDIVS RVFVS, Cr 463/1; #1
9.97
3.79
0.380
Denarius, MN.CORDIVS RVFVS, Cr 463/1; #2
10.20
3.62
0.355
Silver nugget
10.12
6.88
0.680



SpGr
% Gold
Wt, air
Wt, water
11.95
27.0
2.51
0.210
11.41
17.2
2.51
0.220
10.96
9.0
2.52
0.230
11.38
16.6
2.56
0.225
12.05
28.5
2.53
0.210
8.68

4.86
0.560
9.97

3.79
0.380
10.20

3.62
0.355
10.12

6.88
0.680


 Note that the test is sensitive to the weight in water measurement. This may below where my scale gives good results. I think the results are good enough to say my coin is electrum. 

Metal
SpGr
gold
19.32
silver
10.49
Copper
8.96
Lead
11.34
Electrum
12.17


The description below is from the previous post with a few changes. 

BRUTTIUM, Carthaginian occupation. Circa 216-211 BC. EL 3/8 Shekel

Based on one letter at 12 on obverse, may be struck over another coin???
Obv - Janiform female heads, wearing wreaths of grain
Rev - Zeus, holding thunderbolt in right hand, scepter in left, standing in quadriga right, driven by Nike, who holds reins.
2.5 g
14.7 X 15.9 mm
12 h
F, light gray / yellow tone, well worn or poorly struck. Rare.

References (note I have the first 4 books, I do not see the coin in Crawford): Two links with more info are below.
Jenkins & Lewis, Carthaginian Gold and Electrum Coins, Group XVI, numbers 487 - 493 (Capua)
1.  J&L mention 47 coins tabulated by Bahrfeldt in Die romische Goldmunzpragung.
2.  SpGr for the 8 coins in Group XVI ranges from 11.99 to 12.34. One coin was mentioned in an addenda that was SpGr = 11.92 and 27%. (Somewhere I read, but can not find now, that the %gold            dropped into the teens late in the war)
HN Italy 2013
Grueber, BMCRR – Romano Campanian Coinage, Half Stater, No 145 – 149
Sear Greek Coins, Vol 1 Europe, 287

SNG Copenhagen 357
Robinson, Punic p. 40 (Capua)
SNG ANS 146 (Capua)





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