The NBMG Rock Garden at GBSSRL

 

What You Might Find in the Rock Garden
at the Great Basin Science Sample and Records Library

  
  The NBMG Rock Garden at GBSSRL  

 

Feel free to take a few pieces for your personal rock and mineral collections, but please take only one of any rock or mineral. Also, please do not move the rocks around too much as you explore, so the grid will still be accurate for others. Some of the rocks are labeled below, with approximate coordinates as shown in the photograph above.

There is some logic to where rocks are located. Volcanic (extrusive igneous) rocks are on the left (mostly columns A and B), and intrusive igneous rocks are on the right (mostly columns D and E). Felsic (silicic) igneous rocks are near the top (mostly rows 1 and 2); mafic (basic) igneous rocks are at the bottom (mostly row 5); intermediate igneous rocks are in between. Ores and metamorphic rocks are mostly in the middle. Metamorphosed ultramafic rocks are at E5. Sedimentary rocks are mostly to the right (columns D and E).

Thank you, and enjoy Nevada’s great and interesting geology!

Click to download a pdf of the Rock Garden descriptions

 

The following list is ordered by approximate location (A1 to E1, A2 to E2, A3 to E3, A4 to E4, A5 to E5)

A1. Rhyolite vitric tuff (VITRIC TUFF), Jackpot, Elko County [Miocene, erupted from above the Yellowstone hot spot ~12 million years old (Ma)]

B1. Flow-banded rhyolite (WASHINGTON HILL), Washington Hill, Storey County [~11 Ma]

B1. Rochester Rhyolite (ROCHESTER), part of the Triassic Koipato Group, Coeur Rochester silver mine, Humboldt Range, Pershing County

B1. Rhyolite ash-flow tuff (WINDOUS BUTTE), partially altered to green celadonite, K(Mg,Fe2+)(Fe3+,Al)Si4O10(OH)2, Windous Butte Formation, Grant Range, Nye County [an Oligocene volcanic-rock reservoir in the Trap Spring oil field in nearby Railroad Valley].

B1. Rhyolite (SPHERULITIC DEVITRIFIED RHYOLITE), (spherulitic devitrified, flow-banded rhyolite), Montezuma Range, Esmeralda County [Miocene]

B1. Rhyolite (EAGLES), Rhyolite [Miocene], volcanic rock with crystals of sanidine, KAlSi3O8, plagioclase, (NaAlSi3O8 – CaAl2Si4O8), biotite, K(Mg,Fe2+)3(AlSi3O10)(OH,F)2, magnetite (Fe3O4 – Fe2TiO4), and quartz, SiO2, Eagles House, northeast of Grimes Point, Churchill County

C1. Porphyritic rhyolite (TUSCARORA), [Eocene] with phenocrysts of plagioclase, (Na,Ca,K)(Al,Si)2Si2O8, quartz, SiO2, hornblende, (Ca,Na,K)2-3(Mg,Fe,Mn)3(Al,Fe)2-1 (Si,Al)8O22(O,OH,F)2, biotite, K(Fe,Mg)3AlSi3O10(OH)2, and sanidine, (K,Na,Ca)(Si,Al)2Si2O8, Tuscarora Mountains, Elko County. This 39 million-year-old rock is approximately the same age as gold mineralization along the Carlin trend and many other major gold-producing areas in Nevada.

D1. Dumortierite (DUMORTIERITE), Al7O3(BO3)(SiO4)3, is the lavender mineral, with andalusite, Al2SiO5, and quartz, SiO2, in this metamorphosed Rochester Rhyolite, part of the Triassic Koipato Group, Lincoln Hill, Humboldt Range, Pershing County. Some samples also have both lavender and blue dumortierite. A few samples have only blue dumortierite and quartz; these are from the nearby Champion mine.

E1. Granite (GRANITE) (Cretaceous), from the shaft dug for the 12.5-kiloton underground nuclear test, 367 meters below the surface, detonated on 26 October 1963, Project Shoal, Sand Springs Range, Churchill County. Minerals include orthoclase, KAlSi3O8, plagioclase, (NaAlSi3O8 – CaAl2Si4O8), quartz, SiO2, biotite, K(Mg,Fe2+)3(AlSi3O10)(OH,F)2, and magnetite (Fe3O4 – Fe2TiO4).

E1. Epidote (THULITE), (green), Ca2Al2FeSi3012(OH), and thulite (pink), Ca2(Al,Mn)3Si3012(OH), from a boulder of hydrothermally altered Cretaceous granitic rock in Quaternary-Tertiary sediments, Warm Springs Valley, Washoe County

A2. Rhyolite Tuff (RHYOLITE TUFF), Several rhyolite tuffs are around this location. Among others are: Nine Hill Tuff, Carson City, Stop 3 on the 2014 Earth Science Week field trip [Oligocene, ~25 Ma].

A2. Tuff of Santiago Canyon (SANTIAGO), erupted from a caldera in central Nevada and deposited in the Virginia City area, later affected by propylitic alteration (characterized by pistachio-green epidote, Ca2Al2FeSi3012(OH), dark green chlorite, (Mg,Fe,Al)3(Al,Si)4O10(OH)2.(Mg,Fe)3(OH)6, here replacing pumice fragments, and white albite, NaAlSi3O8), Virginia City, Storey County [~23 Ma]

B2. Mickey Pass Tuff (MICKEY PASS), [Tertiary] Pumpkin Hollow, Lyon County

B2. Rhyolite breccia (EASTSIDE), [Miocene] Eastside Project, Monte Cristo Range, Esmeralda County

C2. Tuff breccia (Thh), [Tertiary] Panther Valley area, Washoe County

D2. Granodiorite (DONNER), [Cretaceous] part of the Sierra Nevada batholith, Donner Pass area, Nevada County, California

D2. Andesite (ESW'13-1), [Miocene, ~16 Ma] with epidote, Ca2Al2FeSi3012(OH), and pyrite, FeS2, Desert Research Institute, Washoe County, Point 9 on the 2013 Earth Science Week field trip

D2. Gold ore with realgar (REALGAR), (AsS) and calcite (CaCO3), Cortez Hills mine, Lander County. NOTE: on a freshly cut or broken surface, realgar is red, but when exposed to sunlight, it turns orange; to preserve the red color, keep it covered or in a dark place.

D2. Schorl (TOURMALINE), Na(Fe,Mn)3Al6B3Si6O27(OH,F)4, a black tourmaline-group mineral, with quartz, SiO2, and goethite, FeO(OH), Buena Vista Hills, Pershing County

E2. Sandstone-Nevada State Rock (AZTEC), [Aztec Sandstone, Jurassic] Spring Mountains, Clark County

A3. Andesite (GILBERT ANDESITE), [Gilbert Andesite, Miocene] Monte Cristo Range, Esmeralda County

B3. Rhyolite tuff (TOQUIMA), [Oligocene] pieces of diamond-drill core from a gold-exploration project, Toquima Range, Nye County

B3. Tuff of Castle Peak (CASTLE PEAK), [Miocene, ~24 Ma] Monte Cristo Range, Esmeralda County

C3. Nevada Wonderstone (WONDERSTONE), rhyolite air-fall tuff [Miocene], south of Eagles House, Lahontan Mountains, Churchill County, Stop 3 of the 2011 Earth Science Week Field Trip. The rock has been altered by hot waters that deposited pyrite (FeS2) and quartz (SiO2). Rainwater later penetrated the rock and oxidized the pyrite to form liesegang bands of red hematite (Fe2O3) and orange and brown goethite [FeO(OH)]. Miocene volcanoes in western Nevada were part of what is now the Cascade Mountains. This type of hydrothermal alteration is commonly associated with the gold and silver deposits that have been important to Nevada. Nevada, the Silver State, entered the Union in 1864 because its rich silver deposits on the Comstock Lode were needed for the war (hence the mottoes “Battle Born” on the state flag and “All for Our Country” on the state seal). We are currently in the midst of the biggest gold-mining boom in American history. Nevada leads the nation in gold production.

E3. Anhydrite (ANHYDRITE) Ca2S04, metamorphosed Jurassic marine gypsum, Ca2S04.2H2O, from the Adams Claim (Art Wilson Co.) gypsum mine, Virginia Range, Lyon County

A4.Rhyolite (MAJUBA) with quartz, [SiO2] phenocyrsts, K-feldspar [KAl3Si3O8] and plagioclase [NaAl3Si3O8-CaAl2Si2O8] phenocrysts; some samples have malachite [Cu2CO3(OH)2] and azurite [Cu3(CO3)2(OH)2] (Late Oligocene), Majuba Hill, Pershing County

A4. Breccia with fragments of rhyolite with quartz (MAJUBA BX), [SiO2] phenocyrsts, and tourmaline, [Na(Fe,Mn,Li,Al)3Al6B3Si6O27(OH,F)4] replacing K-feldspar [KAl3Si3O8] and plagioclase [NaAl3Si3O8-CaAl2Si2O8] phenocrysts and in the matrix of the breccia; some samples have malachite [Cu2CO3(OH)2] and azurite [Cu3(CO3)2(OH)2] (Late Oligocene), Majuba Hill, Pershing County

A4. Rhyolite with Quartz (MAJUBA TOUR) [SiO2] phenocyrsts, and tourmaline, [Na(Fe,Mn,Li,Al)3Al6B3Si6O27(OH,F)4] replacing K-feldspar [KAl3Si3O8] and plagioclase [NaAl3Si3O8-CaAl2Si2O8] phenocrysts (Late Oligocene), Majuba Hill, Pershing County

B4. Andesite (ANDESITE) [Miocene] from outcrops near the Great Basin Science Sample and Records Library, Nevada Bureau of Mines and Geology, Washoe County

C4. Magnetite, Fe3O4, and apatite, Ca5(PO4)3(OH,F,Cl), Jurassic iron ore from the Buena Vista mine, Buena Vista Hills, Churchill County

C4. Copper-iron ore (PUMPKIN H), [Jurassic] with chalcopyrite (CuFeS2) and magnetite (Fe3O4), Pumpkin Hollow property, Lyon County

D4. Epidote (EPIDOTE), Ca2Al2FeSi3012(OH), mostly from Triassic meta-basalt or meta-andesite, Carson River area, Carson City

D4. Rhyolite (NV PACKARD), part of the Triassic Koipato Group, Nevada Packard mine, Pershing County

D4. Pyrite (RIO TINTO), FeS2, Rio Tinto mine, Elko County

D4. Limestone (NV Hg), [Mesozoic] with veins of calcite [CaCO3], Nevada Quicksilver mine, Humboldt Range, Pershing County

E4. Marble (CARARRA), [Cambrian Carrara Formation], composed mostly of calcite, CaCO3, Carrara quarry, Bare Mountain, Nye County

A5. Basaltic andesite (BASALTIC ANDESITE), (lava flow) with microscopic crystals of pyroxene, Ca(Mg,Fe)Si2O6, plagioclase, (NaAlSi3O8 – CaAl2Si4O8), and magnetite (Fe3O4 – Fe2TiO4) [~1 Ma], north side of Carson City

A5. Basalt (LOCKWOOD), (lava flow) with mostly microscopic crystals of olivine, (Mg,Fe)2SiO4, pyroxene, Ca(Mg,Fe)Si2O6, plagioclase, (NaAlSi3O8 – CaAl2Si4O8), and magnetite (Fe3O4 – Fe2TiO4), [~1 Ma] south of Lockwood, Storey County

B5. Scoria (SCORIA), (basaltic andesite with holes from CO2 and H2O that bubbled out of the lava as pressure dropped upon eruption), [~1 Ma], north side of Carson City

C5. Ferricrete (FERRICRETE), this rock is composed of fragments of other rock (Quaternary colluvium) cemented with iron oxyhydroxide (goethite, FeO(OH)) and iron oxide (hematite, Fe2O3) that precipitated from natural acid-rock-drainage spring water from a nearby mineralized area with quartz (SiO2), alunite (KAl3(SO4)2(OH)6), and pyrite (FeS2). The fragments are hydrothermally altered Miocene volcanic rocks. Age of the hydrothermal alteration was also Miocene, somewhat younger than the age of mineralization on the Comstock Lode. Geiger Grade (Nevada Highway 341), Washoe County.

D5. Gneiss (GNEISS), [Mesozoic], Samples with white feldspar augen (eyes) are from the Ruby Mountains, Elko County; other samples are from Mineral Ridge, Esmeralda County.

D5. Blueschist (BLUESCHIST), (metamorphosed basalt) with glaucophane, Na2(Mg,Fe)3Al2Si8O22(OH)2, Sonoma County, California

E5. Serpentinite (SERPENTINITE), (California State Rock), composed primarily of antigorite [a variety of serpentine, (Mg, Fe2+)3Si2O5(OH)4] and magnetite [Fe3O4] near GPS location 38˚29’05.19”N 122˚14’35.02”W, Capell Valley Road (Route 128), Napa County, California

 

Feel free to take a few pieces for your personal rock and mineral collections, but please take only one of any rock type per person, so that others may collect as well. 

Thank you, and enjoy Nevada’s great and interesting geology!

Jonathan G. Price, Ph.D.
State Geologist Emeritus
Nevada Bureau of Mines and Geology
 E-mail: jprice@unr.edu
Great Basin Science Sample and Records Library
2175 Raggio Parkway
Reno, NV 89512

Updated 21 October 2020