As magma seeped along faults and through sedimentary rock, ores of such minerals as lead and copper precipitated out. (Little, 1986. Pangaeic collision created the schists, gneisses and granite exposed in Connecticut. (DEP,1990)
Connecticut has an interesting history when it comes to mining and quarrying. During the 1800’s, barite was mined in Cheshire. Barite is a heavy white mineral composed of barium and sulphate. Today it is used in paint, glazes and as and additive to fluids used in drilling oil wells. During the 1800’s, it was sometimes used to adulterate flour. It’s white color allowed someone to mix several unnoticed cupfuls into a big bag of flour, to increase its weight and thus the price. (Bell, 1985)
In the Connecticut Uplands, old mines and quarries extracted such minerals as: nickel, tungsten, cobalt, bismuth, arsenic, quartz, feldspar, mica, marble, garnet, clay, natural cement and gemstones. Most of these operations did not yield enough to be profitable and went bankrupt. (Bell, 1985)
Some open-pit marble mines operated from 1734-1923. These yielded limonite from large pockets in the surrounding marble. Limonite is chemically similar to rust and was easy to convert to pure iron.(Bell, 1985)
Another mining operation in Roxbury attempted to extract iron from the ore siderite, but it was hard to refine and this operation only lasted from 1867-1872. (Bell, 1985) This is a great field trip though, as its blast furnace still exists. Also, one can collect siderite, quartz crystals and garnets (our state mineral) from the area and it is an enjoyable hike. The mining operations for iron, due to the charcoal needed for the blast furnace severely defoliated the area, though today it has recovered. (Bell, 1985)
In the past, one of the most popular building stones in Connecticut was brownstone was quarried from the Portland formation located in the Newark Terrane of the Central Valley. This rock in reality is ferruginous sandstone. (U.S.Dept. of the Interior,1994)
The brownstone industry at its peak in 1880, employed more than 1500 workers and shipped the stone to New York, New Jersey and as far away as California. Brownstone is only minimally quarried today. (U.S. Dept. of the Interior, 1994)
At Lantern HIll Mine in North Stonington, quartz is still actively mined. It is used for building stone aggregate, gravel roofs, pool filters and aquarium gravel. Also, feldspar is still quarried in the Middletown/ Portland area. This mineral is used in making glass, ceramics and part of a wallboard compound. (Bell,1985)
Marble from Connecticut makes up the mantel in the East Room of the White House. Stony Creek granite is shipped all over the country. (Little, 1989) Connecticut’s most valuable mineral today is traprock (basalt). It is prominently seen along I-91 between New Haven and Hartford. (Skinner, 1980)
Traprock is turned into crushed stone. It is primarily used in construction and the in the bedding of roads. (Bell,1985)
Sand and gravel from glacial till is the second most profitable quarried rock. They are used as fill, in concrete, leach fields or for road sand.(Little, 1989) The mineral industry in Connecticut as of 1993, employed 650 workers.( U.S.Dept. of the Interior, 1994)
Gemstones such as amethyst, aquamarine, topaz and emerald are periodically found in our state too. While looking in old rock dumps for tailings can be a haven for collectors, the best finds are usually due to construction and blasting. As previously mentioned, the dinosaur trackway was uncovered during bulldozing. Footprints were recently found at a construction site near Lake Saltonstall in Branford.
A construction site in Trumbull has in the past three years yielded the following mineral: fluorites, pyrite, quartz (both crystalline and massive), topaz,scheelite, beryl and many other minerals. Some specimens have been gem quality. I have taken the Science Club here, but an easier site would be Old Mine Park, which was an area that used to be mined for tunsten. The par!c has most of the minerals found at the construction site in the old mine dumps. The construction site will be covered over with asphalt within the next year.
If you would like to build up a school’s collection one suggestion would be to join your local mineral club. They obtain access to many unknown or restricted sites. Another resource would be a building stone supplier, where you can get minerals such as pumice or limestone for under 35 cents a pound. I know a professor who takes elementary school groups there for a field trip.
The geology of Connecticut can be a fun and exciting subject for students to learn about. It is an ongoing process, with erosion still changing the landscape, continental plates moving, the future possibility of glacial returns and the discovery of more and unusual minerals being found. My lessons plans attempt to be a mixture of the geologic processes that have shaped and will shape Connecticut’s landscape. Also, included are some hands-on activities to demonstrate certain geological principles. As previously mentioned, this unit is meant to be taught after general geology has been covered, so certain assumptions have been made as to the student’s level of knowledge.