1786

It's not known if or at what price the priest actually sold his platina ore in Cadiz. Given the standard trans-Atlantic markup in 1806 was 100%, port-to-port, for commodities from Terra Firma.   

 Where 1 Onza = 0.9246 Ozt, the alleged Pt Price seems impossibly high, higher than Gold:

1786: 1 Ozt platina (Hypo. Lima Spot, 70%) ~ S$ 8.65
1786: 1 Troy Ounce platina (Cadiz Ask, 70%) = S$ 17.30
1786: 1 Ozt. Pt (Cadiz Ask, .999) = S$ 24.72
1786: 1 Ozt. Platinum (Cadiz: Refining Cost) = S$
1786: 1 Ozt. Platinum (Hypo. Spanish Platinum, First Cost) = S$ 
 
Presuming error, alternative Cadiz Ask Prices might be  
a) '16 Reales de Plata per Onza'  
b) '16 Reales de Velon per Onza' 
 
or 1 Onza/ S$8.50 = 0.9246 Ozt,
1786: 1 Ozt platina (Hypo. Lima Spot, 70%) ~ S$ 0.540774
1786: 1 Troy Ounce platina (Cadiz Ask, 70%) = S$ 1.081549


1789:

1. In 1786, the chaplain of the "Achiles" a registered ship from Lima, brought to Cadiz about 1,000 onzas of platina, which he tried to sell at 16 pesos per onza; the chaplain returned to Lima in the same registry and probably with his platina because the price was not really cheap.




See Prof. Luis Fermin Capitán Vallvey's 'The Transport of Platina to Spain in the Late Eighteenth Century' in Platinum Metals Rev., 1999, 43, (1), 31: 

"Only two official shipments were sent from the Kingdom of Peru, and although there were others they are more difficult to identify because of their clandestine nature. Known examples include the one thousand onzas of platina that the chaplain attempted to sell to the El Achiles Register in 1786, and the four boxes of platina sent by Roque Aguado but seized on the instructions of Minister Valdês when they were put on sale in 1787."

Donald McDonald : "About 150 libras of native metal were shipped to Spain, this time the miners being paid two or three reales per libra. Further shipments necessitated the price being raised to four reales per libra"

1786: 1 Troy Oz. platina (Colombian Spot) = S$ 0.0169 - S$ 0.0254

1786: Don Fausto describes Chabaneau refining cost of Platinum, per libra (14.792 Ozt)

"We estimate that the expenses would be less than 4 pesetas (8 reales or 1 Spanish Dollar) per libra and we believe that the metal will find a ready market at a much higher price than that of Silver"

1786: 1 Troy Oz. Pt Refining Cost (Est. Madrid Cost) ~ S$ 0.0676

Cited by LF Capitan Vallvey  in "Export and Smuggling of Spanish Platina"in Annals of Science p. 477:
 

1786: 1 Troy Oz. platina (Paris mkt)= L.T. 5.08 - 6.09 (£ 0.2258 - 0.2707)


1/3/1786: Thomas Jefferson, Paris