LIMESTONE

 

In the commercial decorative stone trade, “marble” is used to refer to a wide variety of relatively soft rocks (H = 3 to 5) that will take a fine polish.  These include true marbles and rocks that aren’t marbles, such as limestones, tectonic breccias, and serpentinites.  Shown below are some limestones used as commercial “marble”.  Limestones are calcitic biogenic and ~chemical sedimentary rocks.

 


 

Jerusalem Limestone (field of view ~5.0 cm across) - a fossiliferous oolitic limestone, widely used for centuries as a building stone in Jerusalem, Israel.  Several Cretaceous-aged marine limestones in Israel have been & are quarried for building/decorative stone.  Light from the setting sun results in these rocks having the famous “Jerusalem Gold” color.

The sample shown above & below is a buff-colored, fossiliferous oolitic limestone.  Yaacov Arkin of the Israel Geological Survey has kindly identified this rock as likely being "Mizzi Hilu" (= “sweet rock” in Arabic) from the Zihor Formation (upper Judea Group, Turonian, lower Upper Cretaceous).

The small rounded structures in the limestone are oolites.  The narrow, curvilinear structures are shells and shell fragments.  The brownish, EKG-looking structure near the top of the above photo is a stylolite (pressure-solution feature).

 

Jerusalem Limestone (field of view ~17.5 mm across).

 


 

Frosterley Marble (12.5 cm across) - a fossiliferous limestone from Rogerley Quarry at Frosterley, Durham County, northern England.  The large, light gray-brown colored, rounded objects in the rock are fossil rugose corals (“horn corals”) - Dibunophyllum bipartitum (M'Coy, 1849) (Animalia, Cnidaria, Anthozoa, Rugosa, Streptelasmatina, Zaphrenticae, Aulophyllidae).  This coral species is commonly encountered in the Great Limestone, a lower Upper Mississippian unit (upper Visean Stage/upper Asbian Stage, Lower Carboniferous, ~329-330 million years) in northern England.

 


 

Black & Gold Marble - a Triassic black micritic limestone from northwestern Italy that has been extensively fractured (with white calcite vein fillings), stylolitized, and partially dolomitized (the yellowish-brown material).  This rock is derived from the Portoro Limestone of the La Spezia Formation (Rhaetian Stage, upper Upper Triassic, ~200-204 million years old), from exposures in the Tuscan Nappe of Italy's Apennine Fold & Thrust Belt.  It's quarried at Porto Venere in eastern Liguria, northwestern Italy.

 


 

Here's a pinkish stylolitized fossiliferous limestone with nice abundant fossil snail shells.  I don't know the commercial name or the provenance (if you recognize this, please let me know).  The stylolite is the reddish irregular line near the bottom.  Stylolites are the result of pressure solution.  They are often present in limestones and marbles in & near orogenic belts.

 


 

Rosso Verona Marble (a.k.a. “Red Verona Marble”) - a hematitic, stylolitized, nodular limestone from the Jurassic of Verona Province in northern Italy.  The lighter-colored areas (nodules) have been attributed to soft-sediment deformation (Pivko, 2003).  Some samples have fossil ammonite shells (Mollusca, Cephalopoda, Ammonoidea, Ammonitida).  This limestone represents part of a condensed succession of sediments deposited on an ancient submarine plateau, the Trento Plateau.

Stratigraphy & Age: Rosso Ammonitico Superiore Member, Rosso Ammonitico Formation, Oxfordian Stage, lower Upper Jurassic.

Locality: commercial quarry near Caprino Veronese or Cerro Veronese or Erbezzo or Sant’Ambrogio di Valpolicella, Verona Province, western Veneto Region (Venetia Region), southern Alps, northern Italy.

 


 

Lapis Eyes Limestone - a lazuritic-pyritic fossiliferous limestone from the famous Flor de los Andes Lapis Lazuli Deposit in central Chile.  The gray material that makes up the bulk of this rock is marine fossiliferous limestone of Early Cretaceous age.  It has been metamorphosed twice during the Tertiary:

1) contact metamorphism by intrusion of monzogranites of the Río Las Cuevas Granite (late Late Oligocene, 24 Ma);

2) sulfur-metasomatism by intrusion of dacites and rhyodacties of the Portezuelo del Azufre Intrusion (late Middle Miocene to Late Miocene, 9-13 Ma).

Neither of these metamorphic events has converted the limestone to marble.  The sulfur-metasomatism event resulted in the formation of blue lazurite and brassy-gold pyrite (= most of the very dark gray spots in the above photo).  Lazurite is a rare metamorphic mineral ((Na1.5K0.2Ca1.2)(Al5.5Si6)(SO3,Sx,Cl1-x)).  Rock-forming lazurite occurs at this locality - lapis lazuli.  Afghanistan’s Hindu Kush Mountains are famous for having the highest-quality lapis lazuli on Earth, but the Chilean deposit also has high-quality material.  The perceived lower-quality material is cut & polished into decorative stone, like this sample.

Stratigraphy & Age of Host Limestone: Río Tascadero Limestone, Berriasian Stage to possibly Barremian Stage, lower Lower Cretaceous.

Locality: Flor de los Andes Mine, in or near glacial cirque at the headwaters of Lapislázuli Creek (a tributary of the Tascadero River), southeast of Ovalle & northwest of Illapel, Coquimbo Region, Andes Mountains, near the border with Argentina, central Chile (~31ľ 14’ 50.52” South, ~70ľ 32’ 10.73” West).

 


 

 

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