The Bayfield group is a

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

found in Wisconsin along the

Lake Superior Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...

coast.Bulletin 1912, p. 25 It is named for the village of

Bayfield, Wisconsin Bayfield is a city in Bayfield County, Wisconsin, United States. The population was 584 at the 2020 census. This makes it the city with the smallest population in Wisconsin. In fact, for a new city to be incorporated today, state regulations re ...

,Eckert, p. 31 but was once known as Western Lake Superior Sandstone. Prior to the 1900s, Bayfield group sandstone was also variously named Lake Superior Sandstone, brownstone, or redstone,Eckert, p. 33 and prefixed by the quarry location. The name was changed to the Bayfield group as its relation to

Jacobsville Sandstone Jacobsville Sandstone is a red sandstone formation, marked with light-colored streaks and spots, primarily found in northern Upper Michigan, portions of Ontario, and under much of Lake Superior. Desired for its durability and aesthetics, the sand ...

(once known as Lake Superior Sandstone) is uncertain.

Formation

The Bayfield group is irregularly bedded, in contrast to the even,

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

sandstones in southern Wisconsin.Bulletin 1912, p. 29 The

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

is entirely devoid of fossils.Bulletin 1912, p. 32 The Bayfield group overlies the much thicker

Oronto Group The Oronto Group is a thick group of arkose sandstone and shale located beneath the Bayfield Group in northern Wisconsin,Bulletin, p. 48. along the northwestern side of the Keweenaw Peninsula and southern Isle Royale, and believed to extend into ...

.Bulletin 1912, p. 48 The formation, 4300 feet thick, is divided into three: ''Chequamegon Sandstone'', ''Devils Island Sandstone'', and ''Orienta Sandstone''. The ''Chequamegon Sandstone'' is a red and white sandstone 1000 feet thick. The ''Devils Island Sandstone'' is a 300-foot thick, pink-to-white pure quartz sandstone with significant ripples. The ''Orienta Sandstone'' is 3000 feet thick and similar to the ''Chequamegon Sandstone'', but with a higher feldspar concentration. The Bayfield group is a member of the Keweenawan Supergroup.

Properties

The Bayfield group is a predominantly red sandstone, though it varies through lighter colors such as pink, yellow, light brown, gray and white.Bulletin 1912, p. 26 A minority portion is a dark "brownstone" which is a good building material. The colors occur in bands, though mottling and other irregular markings are common.Bulletin 1912, p. 31 As most of the stone's constituents are the end-products of

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

, it is very resistant to atmospheric action.

Composition

The grains vary from coarse pebbly grits to shale. The finer the grains, the darker their color. The grains are cemented primarily by quartz, with iron oxide coating the grains. In order of abundance, the Bayfield group is composed of: quartz,

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

(both orthoclase and

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

, iron oxide (both

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

and

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

, and

ferromagnesian A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

minerals. The quartz usually comprises about 75% of the stone.Bulletin 1912, p. 27 Based on an average of 52 samples, the ''Orienta Sandstone'' is composed of: 33.3% nonundulatory quartz, 29.7% undulatory quartz, 17.3% potassium feldspar and 9.4%

silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the group ...

volcanic clasts. Smaller constituents are 3.9% polycrystalline quartz, 2.3% opaques, 1.6% mafic volcanic clasts, 0.9% metamorphic, 0.7% sedimentary, and 0.4% plagioclase. The heavy mineral suite of ''Orienta Sandstone'' is 78% ilmenite, 13% leucoxene, 3-4%

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...

, 3%

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...

, 2%

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...

, and 1%

tourmaline Tourmaline ( ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors. The ...

.Eckert, p. 34

Economic use

The only product that Bayfield group sandstone was used for, the "brownstone" in particular, was building stone.Bulletin 1912, p. 45 In the mid-1860s,

brownstone Brownstone is a brown Triassic–Jurassic sandstone that was historically a popular building material. The term is also used in the United States and Canada to refer to a townhouse clad in this or any other aesthetically similar material. Type ...

was popular in the eastern United States.Bulletin 1912, p. 46 The discovery of the Bayfield group, similar to Eastern brownstones, brought immediate exploitation, and the first quarry opened in 1868 on

Basswood Island Basswood Island is a Wisconsin island in Lake Superior. It is one of the Apostle Islands and a part of the Apostle Islands National Lakeshore. From 1865 to 1923, the island was home to a farm run by Richard McCloud and Elisha Brigham. It was also ...

, operated by the Basswood Island Brownstone Company.Eckert, p. 57 A few years prior to 1893, the business was booming. However, the heavy influence of speculators helped lead to a decline that paralleled the

Panic of 1893 The Panic of 1893 was an economic depression in the United States that began in 1893 and ended in 1897. It deeply affected every sector of the economy, and produced political upheaval that led to the political realignment of 1896 and the pres ...

. By the time that the quarries could recoup their losses, paler limestones had gained favor, partly due to the "White City" of the Chicago World's Fair of 1893. By 1897, very little stone was being extracted. By 1912, only two quarries remained producing high quality Bayfield group sandstone.

Notes

References

* *{{cite book , title=The sandstone architecture of the Lake Superior region, last=Eckert, first=Kathryn Bishop, year=2000, publisher=Wayne State University Press, isbn=978-0-8143-2807-1, url=https://books.google.com/books?id=b68xzUc0y3IC, access-date=18 August 2011 Building stone Geologic groups of Wisconsin