Liberty Pit Mural Rock Display - Nevada - Rock and Mineral Displays on Waymarking.com

Group of 5 boulders with descriptive signs in front of the Liberty Pit Mural at parking lot on the SE corner of Aultman St. & 4th St.
Text of display signs:

Silicified Limestone
This boulder was once a gray limestone. It is now silicified, converted to quartz, as a result of the passage of hydrothermal ore fluids rich in silica through the original limestone. Veins of quartz that criss cross the boulder are further evidence of the movement of those fluids through the rock. If you look very closely, you can see a few scattered patches of fine-grained green garnet created by similar fluids.

Copper “Oxides”
“Copper oxide minerals” such as pale blue chrysocolla (a hydrous copper silicate) are common in near-surface copper ores that were exposed to rain and/or shallow ground waters. These minerals formed from the oxidation of “primary” copper minerals (those formed earlier than the deposit was initially formed and deep beneath the surface). The most common primary copper mineral in the Robinson District is Chalcopyrite, a brass-colored, copper-iron sulfide mineral resembling pyrite but softer and with a somewhat yellower hue. Brassy minerals in the quartz veins in these blocks include pyrite (an iron sulfide mineral) and perhaps minor amounts of Chalcopyrite. Some black magnetite (an iron oxide mineral) is also present here.
The term “copper oxides” is commonly used in the minerals industry to refer to many different secondary copper minerals formed by the weathering and oxidation of primary minerals, but these “oxides” actually include oxides, silicates, carbonates, sulfates, and other types of copper minerals as well. Most of the past and future production of copper from the Robinson District has come not from “oxide ores”, but rather from the treatment of sulfide ores containing chaleocite (a dark, bluish-gray, copper sulfide mineral) and/or Chalcopyrite. Scattered “copper oxide” minerals are also locally present.

Quartz Monozonite Porphyry
This granite-like rock formed from the cooling and solidification of the magma that produced the ore deposits here in the Robinson District. Large pinkish K-feldspar crystals, white plagioclase feldspar crystals, black biotite and/or hornblende, and smoky-gray, glassy crystals of quartz are the main minerals present. Because this rock is thoroughly fractured throughout the Robinson District large boulders of it generally do not occur.

Pyroxene Skarn
These blocks are rich in green pyroxene and green actinolite, two calcium rich silicate minerals that are common in some skarns*. Actinolite is a later-formed mineral, which forms as a replacement of the earlier-formed pyroxene. Often the actinolite has a darker green color and it is very difficult to distinguish the minerals from one another with the naked eye. Veins cutting these blocks also contain white quartz (a silica mineral), black magnetite (an iron oxide mineral), and brassy pyrite (an iron sulfide mineral).
The formation of a skarn is a rock that consists mostly of calcium silicate minerals, such as green garnet. A skarn commonly forms limestone, a rock in which the original minerals were mostly calcite (calcium carbonite).

Breccia
Breccia is a relatively uncommon type of rock consisting of many angular fragments of other rocks. The fragments are mostly gravel-sized pieces of limestone, shale, and their altered products. This Breccia was probably formed by the explosive release of copper-bearing and/or gold-bearing hydrothermal fluids from the quartz monzonite magma into the limestone and shale of the district. You can see many small specks of brass-colored pyrite (also known as “fool’s gold”) throughout the Breccia.

Type of Display: Geological

Visit Instructions:
When posting a visit, please provide at least one photo - including yourself in one of of the photos, your GPSr, or a photo different than the default photo.
Also, please provide your impression of the specimen or display.

Recent Visits/Logs:

Date Logged Log   10/02/2016 Volcanoguy visited it