AZURITE AT GOLD HILL

GOLD HILL ORE CHUTE

I recently noted the occurrence of the occurrence of adamite, a zinc arsenate hydroxide, in my miniscule collection of minerals from Gold Hill, Utah.  A couple of readers (wow, I didn’t know if anyone read these blogs or not ) confirmed the mammillary structures are goethite pseudomorphs after smithsonite!  Another reader suggested that the tiny acicular spray in the vug might be olivenite, a copper arsenate hydroxide [Cu₂(AsO₄)(OH)] that is common at Gold Hill.

In examining tiny pieces of minerals in my collection box I did notice “some blue” color.  I may be color blind with red-green-brown but can spot blue or purple (but I get them mixed up).  Initially I thought the streaks were linarite as a crust rather than small clusters of crystals.  Linarite is a secondary lead copper sulfate hydroxide that is found in the oxidation zone of ore bodies containing lead.  It has that beautiful azure blue color.

CRUST OF AZURITE WITH BOTRYOIDAL HABIT (TOUGH TO SE WITH THIS POWER).  LEFT TO RIGHT IS ~6.2 MM.

However, under high power of my binocular microscope I was able to notice a botryoidal habit rather than tiny crystals common to linarite.  This revived my brain cells and caused me to pull out the acid and I noticed the blue mineral “fizzed” indicating a carbonate.  So, I am now “guessing” (that is what paleontologists do with mineral identification) that the blue streak is common azurite, a carbonate of copper [Cu₃(CO₃)(OH)₂)], with a beautiful azure blue color.  So it goes.

By the way, the Rockpick Legend Co. in Salt Lake City has a wonderful collection of Gold Hill minerals and a great web site at:  

http://www.rocks4u.com/gold_hill.htm

mike

PHOTOMICROGRAPH OF AZURITE CRUST FROM GOLD HILL.  tHE FIELD OF VIEW IS ~2.4 MM.