Portuguese Coin - 1 Escudo - 1962
Catarina. Cordeiro (Universidade Católica Portuguesa, Porto, Porto, Portugal)
Portuguese coin (Escudo from 1962) with brown and green corrosion products. Dimensions: about 2.7 cm in diameter.
coin
Lisboa, Portugal
Unknown
Modern Times
20th century
Unknown
Cordeiro Lopes Catarina, Porto
Cordeiro Lopes Catarina, Porto
None
N/A
None.
The schematic representation below gives an overview of the corrosion structure encountered on the coin from a first visual macroscopic observation.
| Stratum | Type of stratum | Principal characteristics |
| CP1 | Corrosion product | Cluster, dark green, medium, isolated, compact, very soft |
| CP2 | Corrosion product | Layer, dark brown, thin, discontinuous, compact, soft |
| CP3 | Corrosion product | Layer, brown, thin, discontinuous, compact, soft |
| M1 | Metal | Light grey, metallic, continuous, compact, hard |
Table 1: Description of the principal characteristics of the strata as observed under binocular and described according to Bertholon's method.
No sample was taken.
Cu Zn Ni
Unknown
None
None
None.
Analyses performed:
Non invasive approach
- XRF with handheld portable X-ray fluorescence spectrometer (NITON XL3t 950 Air GOLDD+, Thermo Fischer®). General Metal mode, acquisition time 60s (filters: Li20/Lo20/M20).
The XRF analysis was carried out without sampling. All strata, from corrosion products to metal, are analyzed at the same time. The metal is presumably an alpacca (German silver), while Si, Cl, S and P probably originate from the burial environment.
|
Element |
Mass % |
|
|
Cu |
61 |
|
|
Zn |
17 |
|
|
Ni |
16 |
|
|
Si |
3 |
|
|
S |
<0.5 |
|
|
Fe |
<0.5 |
|
|
P |
<0.5 |
|
Table 2: Chemical composition of the surface of the coin. Method of analysis: XRF, UR-Arc CR.
None.
Unknown
Cu
Ni, Zn
According to the Catalogue "Moedas Portuguesa e do Território que hoje é Portugal" (Portuguese Coins and the Territory that is now Portugal) [1] and because it is a coin verified by the Mint, it is possible to state that the present alloy is an alpacca (Cu, Zn, Ni). The composition as given by Gomes [2007] should be:
| Element | % |
| Cu | 61 |
| Zn | 20 |
| Ni | 19 |
Table 3: Composition of the coin according to Gomes, 2007 [1].
It appears from table 2 that the concentrations of Zn and Ni are slightly higher than expected.
The coin presents 3 types of compounds, two with brown tones that occupy most of the surface and one with a green tone (copper-based compound) that is locally distributed and which could be due to chlorides (handling).
Unknown
Unknown
None.
None.
The coin under study is recent (1962). From literature, it should be alpacca also known as German silver. It was confirmed through non invasive XRF anaalysis.
Regarding the corrosion products, the coin presents 3 types of compounds, two with brown tones that occupy most of the surface and one with a green tone (copper compound) that is localised and could be due to handling (chlorides were detected).
References on object
1. Gomes, A, Moedas Portuguesas e do Território que Hoje é Portugal, 5th edn., Associação Numismática de Portugal, 2007, pp. 399.
