An arrastra (or arastra) is a primitive
mill for grinding and pulverizing (typically)
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
or
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...
. Its simplest form is two or more flat-bottomed drag stones placed in a circular pit paved with flat stones, and connected to a center post by a long arm. With a horse, mule or human providing power at the other end of the arm, the stones were dragged slowly around in a circle, crushing the ore.
Some arrastras were powered by a
water wheel
A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...
; a few were powered by steam or gasoline engines, and even electricity.
[
Arrastras were widely used throughout the Mediterranean region since ]Phoenicia
Phoenicia () was an ancient thalassocratic civilization originating in the Levant region of the eastern Mediterranean, primarily located in modern Lebanon. The territory of the Phoenician city-states extended and shrank throughout their histor ...
n times.[ The Spanish introduced the arrastra to the ]New World
The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. 3 ...
in the 16th century. The word "arrastra" comes from the Spanish language
Spanish ( or , Castilian) is a Romance languages, Romance language of the Indo-European language family that evolved from colloquial Latin spoken on the Iberian peninsula. Today, it is a world language, global language with more than 500 millio ...
''arrastrar,'' meaning to drag along the ground.[ Arrastras were suitable for use in small or remote mines, since they could be built from local materials and required little ]investment capital
In economics, capital goods or capital are "those durable produced goods that are in turn used as productive inputs for further production" of goods and services. At the macroeconomic level, "the nation's capital stock includes buildings, eq ...
.
For gold ore, the gold was typically recovered by amalgamation
Amalgamation is the process of combining or uniting multiple entities into one form.
Amalgamation, amalgam, and other derivatives may refer to:
Mathematics and science
* Amalgam (chemistry), the combination of mercury with another metal
**Pan am ...
with quicksilver. The miner would add clean mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
to the ground ore, continue grinding, rinse out the fines, then add more ore and repeat the process. At cleanup, the gold amalgam was carefully recovered from the low places and crevices in the arrastra floor. The amalgam was then heated in a distillation retort to recover the gold, and the mercury was saved for reuse.[
For silver ore, the patio process, invented in Mexico in 1554, was generally used to recover the silver from ore ground in the arrastra.
]
References
External links
*
Arrastra
at Encyclopædia Britannica
The (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various time ...
{{Extractive metallurgy
History of mining
History of metallurgy
Mining equipment
Grinding mills