Re: how augite is mined

Hello!

I see you're from Wisconsin (or, at least, "Wi" is the state abbreviation on
the little email that comes with the question).  So let me get you started 
on this by noting the following website: 

        http://www.uwrf.edu/~wc01/augite.htm 

This is a part of the general website of the University of Wisconsin at 
River Falls, and there is good deal of information there about augite in
Wisconsin, its county-by-county occurences, etc.

Augite, as you probably already know, can be a main component of certain
massive igneous, esp. basaltic, rocks, or it can occur in somewhat rarer 
environments like skarns made from carbonate rocks intruded by silicate- 
bearing fluids (be they magmatic, hydrothermal, or whatever).

From what I can glean, the mining of augite is more or less in two forms.
For the massive type, quarrying is the common method, with the main 
objective being such items as crushed rock for building and roadbeds, or
block-type building stone. This kind of quarrying is, as far as I know, no 
different than that used for quarrying a lot of types of stone. A field trip 
to a quarry will probably teach you a ton more than I can about the actual, 
on-site practical aspects of the industry. From the rarer environments like 
the skarns, the objective seems to be the fine crystals that can be found in 
them. Here the mining tends to be much smaller scale and  less violent than 
that for quarrying. While there may be some gangue removal by blasting, this 
is usually kept to a minimum and at minimum strength, because such blasts 
can shatter the sought-after crystals. Usually, such mining proceeds until 
pockets (essentially cavities or fissures in the host rock) are found. These 
are then generally mined quite carefully by hand to remove the crystal 
groups without damage.  While I have not seen many specimens of augite
proper on the mineral market, its close cousin diopside (especially the
deep green chromian variety) is reasonably often seen and some of the
crystal groups are breathtakingly beautiful. Chromian diopside can rival or 
exceed emerald in the glory of its green coloration, and is often found with 
far fewer inclusions and defects as well. It makes magnificent gemstones, 
yet is little known in the gem trade.