Pre-Columbian Peruvian Metals (2 samples)

Sample 17a

Solid Beads

Chimu

North Coast, Peru

ca. 900-1100 AD

Report by :

Kristen Willard

May 14, 2003
Introduction (sample A)
Figure 1: Ornamental Beads
  
This Peruvian sample is Chimu in origin, dating approximately A.D. 900-1100. The Chimu society dominated northern Peru from 1000 to approximately 1470 A.D., immediately following the Moche period. The capital city was Chan Chan. The Chimu society was known for a strong administrative and economic system, especially concerning trade, production, land, water, labor and religion. Burial platforms were important to the direction of their architecture and administrative offices. Pottery was mass-produced and decorated by molded metals. Most metal objects were also produced with a mold, though they were more complex than the pottery. In A.D. 1470, they were conquered by the Inca. Peruvian silver was abundantly produced at the time.
Proceedure  
The following procedure was followed in preparing and etching the Peruvian sample. It was used whole; there was not a piece cut from it to be analyzed. To mount the sample, it was placed in the open end of a plastic mount and placed in the bottom of a clean green cartridge coated with release agent (which would prevent the resin from sticking to the sides). Then the resin solution was mixed - it contained a 1:5 ratio of hardener to apoxy resin, and was mixed for approximately three minutes. Labels were pressed onto the sides of the cartridge, and the resin was poured directly over the sample until it was completely covered. The filled cartridge was placed into a vacuum to release any air bubbles, and then it was allowed to dry for 24 hours under a hood.
The sample then had to be thoroughly polished. For this particular sample, it was first run over a 6 micron diamond sanding sheet (with hyprez diamond paste and diamond lubricant), then one micron with a 1mol solution of Al2O3, and a 0.3 micron sander with a 0.3 molar solution of Al2O3, then run on the master prep with silicon dioxide. In between each stage, the sample was rinsed with water, then ethanol, and dried under a hand-blower. There was much difficultly experienced polishing the sample well. There were often many scratches, no matter how long it was on the silicon dioxide. In the end, it was run one more time on the 1 micron, then by hand on the 0.3 micron, and then on silicon dioxide for at least 20 minutes.
After the sample was completely polished, it was etched to reveal the patterning of the base materials. To etch the bead, it was dropped in a alcoholic ferric chloride solution (120 mL ethanol, 30 mL HCl, and 10g ferric chloride) for three seconds, rinsed under water, and set in an ethanol sonic vibrator for approximately one minute. Photographs were taken of the sample before and after, for analysis.
Figure 2: Slight gold enrichment at outer surface, note heavy working of object.
Figure 3: not jointing, lack of solder.
Results  
Looking at the SEM, the sample was mainly silver. The edges would indicate depletion gilding, however, since the place of welding is not quite all the way around, it was formed and then gilded. Also, gold tends to kind of melt together when 2 pieces are hammered together, and the joint part here is definitely not that, so it was depletion gilded after, or there is a very low content of gold in it.
Figure 4: Note the gold enriched surface.

 

Pre-Columbian Peruvian Metals (2 samples)

Sample 17b
Introduction (Sample B)  
This peruvian sample is Chimu in origin, dating approximately A.D. 900-1100. The Chimu society dominated northern Peru from 1000 to approximately 1470 A.D., immediately following the Moche period. The capital city was Chan Chan. The Chimu society was known for a strong administrative and economic system, especially concerning trade, production, land, water, labor and religion. Burial platforms were important to the direction of their architecture and administrative offices. Pottery was mass-produced and decorated by molded metals. Most metal objects were also produced with a mold, though they were more complex than the pottery. In A.D. 1470, they were conquered by the Inca. Peruvian silver was abundantly produced at the time.
Proceedure

The following procedure was followed in preparing and etching the Peruvian sample. It was used whole; there was not a piece cut from it to be analyzed. To mount the sample, it was placed in the open end of a plastic mount and placed in the bottom of a clean green cartridge coated with release agent (which would prevent the resin from sticking to the sides). Then the resin solution was mixed - it contained a 1:5 ratio of hardener to apoxy resin, and was mixed for approximately three minutes. Labels were pressed onto the sides of the cartridge, and the resin was poured directly over the sample until it was completely covered. The filled cartridge was placed into a vacuum to release any air bubbles, and then it was allowed to dry for 24 hours under a hood.
The sample then had to be thoroughly polished. For this particular sample, it was first run over a 6 micron diamond sanding sheet (with hyprez diamond paste and diamond lubricant), then one micron with a 1mol solution of Al2O3, and a 0.3 micron sander with a 0.3 molar solution of Al2O3, then run on the master prep with silicon dioxide. In between each stage, the sample was rinsed with water, then ethanol, and dried under a hand-blower. There was much difficultly experienced polishing the sample well. There were often many scratches, no matter how long it was on the silicon dioxide. In the end, it was run one more time on the 1 micron, then by hand on the 0.3 micron, and then on silicon dioxide for at least 20 minutes.
After the sample was completely polished, it was etched to reveal the patterning of the base materials. To etch the bead, it was dropped in a alcoholic ferric chloride solution (120 mL ethanol, 30 mL HCl, and 10g ferric chloride) for three seconds, rinsed under water, and set in an ethanol sonic vibrator for approximately one minute. Photographs were taken of the sample before and after, for analysis.
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This site was last updated on July 25 2003