Ore Shoots

What is an Ore Shoot? Some may think that ore shoots have something to do with guns. Not really. But it may be good thing to carry a gun in bear or mountain lion country when searching for ore shoots. Those bear can move almost as fast as my Honda Fit! An ore shoot is considered a minable part of a vein that has been enriched by one or more structural or chemical processes along a vein or lode - it is essentially the equivalent of a pay streak in a gold placer. After examining the definition reported by Wikipedia, Merriam-Webster, and Lexico, I can see why people get confused over this term, as it is apparent that these three sources on the internet have little understanding of ore shoots. Is it just me, or has the internet made a major dumb-down in the past few years. Seems like the internet is starting to Woke and get stupid, just like some of its human counterparts. Mindat is the closest to a good definition of ore shoot, but it needs a little help, and the Free dictionary is the best of these.

Ore shoots are those parts of veins, ore bodies, or mineralized faults that are enriched in mineral values such that it may be minable under favorable circumstances. Ore shoots are surrounded by vein or mineralized rock material of lower value, and can be structurally or chemically enriched, and can be formed of primary or secondary ore, or both. A similar term to 'ore shoot' is ore chute.

Many chemically formed ore shoots yield good ore deposits. During vein formation, hot silica (quartz-rich), hydrothermal acidic fluids react with rocks of favorable chemistry; particularly rocks with calcium carbonate (limestone, dolomite). Thus, while prospecting a vein along trend where it cuts through limestone, could lead the prospector to skarns, replacement deposits, etc in a search for gold, silver, copper and other valuable minerals. Replacement deposits and skarns are often formed when such mineralizing fluids come in contact with limestone or even rocks such as limy shales, or limy sandstones. Replacement deposits can be very rich.

Cupriferous gossan - note the tawny limonite (hydrated iron oxide) with fissures filled with azurite (copper carbonate) typically found in many mining districts in Arizona and Utah, particularly in
leached zones and also in supergene enriched zones. Such zones are commonly found associated
with copper ore in Arizona.

The tan matrix in this specimen invaded fractures in a quartz vein and partially replaced
the quartz.

Imagine you are mining along a mineralized vein for
galena (lead-sulfide), and the material is very low
grade, such as that at Black Buttes, WY (top photo).

Then, over a short distance, the vein is enriched yielding 

a massive galena ore shoot, such as that at the Emma mine, 

Utah (bottom photo).

 

A sample of massive galena from the Lark Mine, Utah. While 
searching for galena, a miner might discover that the
lead-sulfide contains silver within the crystal structure. This
would also improve the value of the ore (or ore shoot), but
the silver would have to be metallurgically extracted from
the crystal structure of the galena. Much galena is used to
manufacture bullets! So, how does one separate lead from 
sulfur, and how does one extract silver from lead-sulfide?