Thursday, June 30, 2016

June Field Trip Report

    Hot! Hot! Hot!  Sound like a mid-June field trip in SW New Mexico?  Yes is the correct answer in case you had any doubts.
    First I have to add a comment on last month's trip to the Grandview Mine.  I did find a reference to gold production at the mine after I sent in the report.  So I just wanted to set the record straight that some gold was produced from the Grandview in its later years of production.

     The June field trip started out with the usual sign-in at the Visitor Center.  A good number of participants turned out for the trip. We all drove out Hwy 180 to the Gila turnoff, drove thru Gila and continued on to the Turkey Creek road.  This area is the Gila Fluorspar mining district which consisted of three mines, the Foster, Clum and Victoria.  The mines produced from the early 1880's (Foster) through the late 1940's.  The ore was used primarily as a flux in smelting of metal ores.  At first it was shipped to Silver City and then during the war efforts it was shipped via truck and rail to processing plants in Deming and Lordsburg until 1943.  The government contracted a mill to be built in Gila at that time.  Most of the ore was then sent to a steel mill in Pueblo, CO.  The Clum mine had a brief resurrection in the 1970's with its ore being used to produce hydrofluoric acid.  All the mines are currently abandoned.

      Fluorite or fluorspar is calcium fluoride, CaF2.  It crystalizes in isometric  forms commonly occurring as cubes and octahedrons.  It also breaks along very distinct cleavage planes.  Colors are commonly clear, purple, blue, green with yellow and pink from some locations.  It is used as a flux in smelting metals; in the manufacture of hydrofloric acid; in the manufacture of glass and enamel; and in jewelry.

      The fluorite veins in the Gila district were deposited along faults and fractures through volcanic latites from the Mogollon volcanic period.  The faulting and mineralization occurred during the development of the Barsin Caldera between 28 to 17 million years ago.

      Our first mine stop, the Foster, was not far from the road.  We all hiked in and started scouring the tailings finding lots of pieces of fluorite glittering in the sunlight. Most were clear, but some were a faint green/blue. Down the hill a little was there was a cut through the rock which lead to a blocked off adit.  HIgh angle veins of fluorite cut thru the bedrock, latite, here and with some arm-strong hammering and prying some nice samples of green and purple banded fluorite were collected.  There was plenty to share with the rest of the group.  A few samples with nice cubic crystals were also found in the area.

     Everyone toted their treasures back to the vehicles and we were off to the next location.  The road was not bad for a dirt road but a bit of a challenge in places for a sedan-type vehicle.  The second stop was touted as a drive-right-to-the-mine site, but most of us opted to park up top and hike down to the the site which wasn't too far.  Again the tailing piles were aglitter with fluorite pieces.  Some folks had great spots that they excavated with great abandon plucking up nice fluorite samples.  Others choose to work on breaking down some boulders with fluorite veins running thru them.  Again some nice samples of green with some purple were collected.  In this area there were some nice, albeit small, samples with octahedral crystal clusters.  Most of these were purple with some clear.  All had a great time hammering boulders into small rocks in the quest for a beautiful sample.

     We then continued on the road stopping at one point for Ansel to out another fluorite mine.  It was an uphill hike and we were all hot and uninterested in exploring the location.  We continued up, over and down, down, down the road into the Gila River valley.  The scenery was stunning coming down into the valley.  At the intersection of the dry creek bed we stopped and hiked to a hot springs.  Something about a hot springs in 100° weather that wasn't too appealing.  We all tested the water temperature water and decided to find the Gila River for lunch and a wade in the cool water.  It was a fine end to yet another fun field trip.