By TERRY WALLACE
Los Alamos

When silver runs as “the blood of the bull”: Chanarchillo. A number of silver species are varying shapes of the color red, and collectively these are commonly referred to as the “ruby silvers”. The distinctive color made the ruby silvers one of the earliest silver ores studied – Agricola wrote about the “argentum rude rubrum” in the 16th century.

The most common ruby silvers are pyrargyrite and proustite (Ag3SbS3 and Ag3AsS3 respectively), and for many mineral collectors these specimens are the ultimate specimens. A fine proustite, with the scarlet vermillion color which required carefully curation, seems to glow. When ruby silvers are encountered in mining, the light of a headlamp seems to capture fresh blood oozing from the rock – and the miners rejoices at finding the blood of the bull.

The world’s greatest mining district for proustite is Chanarcillo, Chile, Between 1850 and 1875 an extraordinary number of terminated, undamaged proustites were recovered in veins of calcite. The largest of these crystals were more than 10 cm in length.

A significant quantity of these crystals were preserved by miners – although it is also true that tons (literally) of proustite were sent to the mill for silver value.

The Chanarcillo deposits are located south of Copiapo, about halfway between Antofagasta dn Santiago Chile, in the Atacama Desert. In May 1832 a freight hauler and prospector named Juan Godoy was hunting llamas when he tired and decided to rest under the shade of an outcrop. Godoy noticed a waxy vein and began to pry some material out with his knife – he later described it as “soft as cheese”. He loaded up two mules with what the assayer recognized as chlorargyrite and headed to Copiapo. Godoy entered a partnership with a merchant, Juan Callejo Miguel Gallo, and together they founded the Descubridora mine.

Rumors of the richness of the strike started a rush to Chanarcillo, and by 1850 there were almost 2,000 miners in the district digging in 2 dozen mines. Figure 2 below shows a drawing of the main hill in Chanarcillo and sprinkled with mine dumps (the date of the figure is 1859). The mines were haphazard, and the district was in a state of constant conflict over ownership of the wealthy veins.

Figure 2 is a drawing of the main hill in Chanarcillo dated 1859.

Figure 3 is an example of a 7.8 cm wire. Photo by Jesse La Plante photography

The Descubridora mine produced the largest and best native-sliver specimens from Chanarchillo. Much of the silver occurred as thick wires enclosed in calcite (figure 3 above is an example of a 7.8 cm wire, Jesse La Plante photography), while the characteristic habit is arborescent “flags” or herringbone plates of crystals (figure 4 below is an example – 6.2 cm tall, Jeff Scovil photograph).

Figure 4 is an example – 6.2 cm tall of native-sliver specimens from Chanarchillo. Photo by Jeff Scovil

Two other mines of note: The Mina Dolores Tercera and the Bolados. During mining in the late 1850s the lower levels of the Dolores encountered a series of vugs with remarkable proustite. Figures 5 and 6 below are reported to have come from these vugs (Jeffrey A. Scovil photographs). Figure 5 below is a massive cluster of crystals that weighs almost 2 pounds! The Bolado mine produced some huge masses of native silver, one of which weighed 1,360 km.

Figure 5 is a massive cluster of crystals that weighs almost 2 pounds. Photo by Jeff Scovil

Figure 6 is reported to have come from the Mina Dolores Tercera. Photo by Jeff Scovil

The score of major mines in Chanarcillo produced about 100 million dollars worth of silver (in 1875 dollars). Most of the mining was abandon by the end of the nineteenth century because the ores were exhausted, although there were periodic attempts to revive the camp throughout the 20th century.

Today, all the dumps in Chanarcillo have been hauled away for processing, and every trace of mineralization has been chipped away from the tunnels and open workings. However, it is possible to descend down a hundred foot staircase carved in limestone in the Mina Dolores. Only a few fragile relics of one of the greatest silver camps in history. #huttonproject