Johnson Sand and Gravel is located in Wisconsin, a region rich in rock and mineral varieties. This is especially beneficial and profitable for miners.

Physical features of the Wisconsin

The topography and physical deposits in the region have largely been affected by the four major stages of glaciation, the last of which ended in the Wisconsin region almost 10,000 years ago.  As a result of this the area was left rich in glacial deposits that form a large part of the topography and physiography even as of today. The most dominant one of these glacial deposits is the Kettle Moraine in the Waukesha County while the rest of the region is covered by a variety of glacial landforms and features including different types of moraines, drumlins, kames, outwash plains and lake basin deposits. The outwash plains are deposits that have been stratified and mainly consisting of gravel, sand, silt and clay laid down by water from melting ice fronts. In addition to these glacial deposits, it’s alluvium, marsh deposits and overlying bedrock that exceeds 100 feet throughout most of the county. Bedrock topography in the region is a result of pre-glacial and glacial erosion of the exposed bedrock. The bedrock formations under the surface deposits of Waukesha County consist of
  • Precambrian crystalline rocks
  • Cambrian Sandstone
  • Ordovician Dolomite
  • Sandstone and Shale
  • Silurian Dolomite

Minerals found in this region

Diamond

A reasonable number of diamonds have been found through the years in glacial drift and river sediments in Wisconsin. While most diamonds form within the earth’s mantle, they are brought to the surface by the action of deep-seated magma and then carried over long distances from its source by rivers or glaciers. In most cases the deposits occur with denser minerals such as magnetite, garnet and gold. The discovery of these drift diamonds in the region suggests that there is a local source for at least some of them. Giving credibility to this claim is also the fact that a 16.5 carat diamond of a warm sunny color was reportedly found by drilling in 1876 near Eagle. The Eagle diamond was in the American Museum of Natural History until stolen in 1964.

Calcite CaCO3 Hexagonal

Calcite, a mineral formed by precipitation from ground and surface waters, is also found in Wisconsin. It forms the major component of marls and limestone in the ocean, lakes and rivers and most of the occurrences of this mineral in the state are in the region underlain by Paleozoic carbonate rocks. Marls that are Calcite rich have been mined by shallow surface pits in the Scuppernong Creek Area.

Dolomite CaMg (CO3)2 Hexagonal

Dolomite is another abundant mineral in Wisconsin State. The main areas where this rock-forming mineral is found are the outcrops in a band reaching outcrops in a band reaching from the lower St. Croix River to the west, south along the Mississippi to the Illinois border, west across southern quarter of the state, and continuing north along the entire Lake Michigan shoreline. The dolomite is believed to be a secondary replacement of original limestone while the sediment was undergoing lithification.

Pyrite FeS2 Isometric

Pyrite, a common sulfide found in many environments is another mineral vastly present in the region. Pyrite occurs abundantly in black shale and interbedded limestone at the Roberts Quarry on the south side of Peawaukee Lake. It is a common accessory mineral in igneous, sedimentary and metamorphic rocks.

Quartz SiO2 Hexagonal

Quartz again, is an abundant mineral and there are only a few regions in the state where it isn’t found. In other words, it’s present in the state in vast quantities. It is an essential component of granitic igneous rocks, of sedimentary rocks such as sandstone and chert and of metamorphic rocks such as quartzites. Quartz also forms the bulk of unconsolidated sediments such as drift and alluvium.

Copper Cu Isometric

Copper deposits similar but smaller in quantity compared to those occurring in the Upper Peninsula of Michigan in Keweenawan are found in Wisconsin state where these rocks extend into Wisconsin through Bayfield, Washburn, Douglas and Polk counties. These have been formed by basaltic lava and interlayered sediments approximately a billion years ago. Nuggets of copper weighing anywhere from a fraction of an ounce up to 6000 lbs. have been found in glacial drift derived from the weathering of this bedrock. This kind of drift copper can be found anywhere in the state and is easily recognized by its bright green to black alteration crust, high density, malleability and brilliant copper color on a fresh surface.

Gypsum CaSO4.2H2O Monoclinic

Gypsum too has a relatively common occurrence in the region. It is found in sedimentary rocks, either as a primary precipitate from sea or saline lake waters or as an alteration of minerals such as anhydrite. It is deposited from groundwater with sedimentary rocks such as shale or limestone. Gypsum also forms from low temperature hydrothermal fluids. It can form during the weathering of sulfides such as marcasite.

Marcasite FeS2 Orthorhombic

Marcasite is common in Wisconsin, often found in well-formed crystals in cavities and veins in the Paleozoic carbonate rocks. It is one of the most abundant minerals in the zinc-lead mines in the southwest part of the state where it forms in low temperature hydrothermal veins associated with sphalerite, galena, pyrite, calcite and dolostones in the Upper Mississippi Valley zinc-lead district. It also occurs commonly in cavities in the Ordovician Prairie du Chien group and in the Silurian Niagara Formation of eastern Wisconsin. Here it occurs as a groundwater precipitate with pyrite, quartz, calcite and dolomite.

Sphalerite ZnS Isometric

This mineral is found in the form of a low temperature hydrothermal deposit and is mainly found in the southwestern portion of Wisconsin. This deposit is mainly in the form of Ordovician Carbonate rock forming gash veins replacement bodies as well as sloping pitches and flats along bedded plains. This mineral has been produced from the district since 1860’s.

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