The description and identification of minerals in Delaware dates from the first quarter of the nineteenth century. During this time, both geologists and amateur mineral collectors have published on the minerals of Delaware including George Carpenter, Issac Lea, James Booth, and Henry duPont. The location of most mineral occurrences in the state occurs in the Delaware Piedmont. This area is comprised on mafic and felsic gneisses and amphibolites of the Wilmington Complex and the metasedimentary gneisses in the Wissahickon, Cockeysville, and Setters formations as well as the migmatitic gneisses and amphibolites of the Baltimore gneiss. The coastal plain contains relatively few mineral localities. These occurrences can be generally divided into those of the oxidizing or oxygen-rich environments of deposition yielding iron oxide deposits and those of reducing or oxygen-poor environments of deposition yielding iron sulfides, phosphates, and carbonates in greensand and organic muds. (Taken from "Minerals of Delaware" by Peter B. Leavens, in 1979, Transactions of the Delaware Academy of Science, 1976, Delaware Academy of Science, Newark, Delaware).

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Special Note

Invalid Mineral Names and Mineral Symbols (per IMA/CNMMN)

• bronzite = var. of enstatite
• canbyite = hisingerite
• deweylite = mixture of layer silicates
• fibrolite = sillimanite
• garnierite = probably nepouite
• hornblende = amphibole group
• eucoxene = most likely anatase or rutile
• limonite = most likely goethite
• marmolite = most likely chrysotile or lizardite (serpentine group)
• picotite = chrome spinel
• psilomelane = probably romanechite
• serpophite – most likely lizardite (serpentine group)
• wad = mixture of Mn oxides/hydroxides

Greensand is composed primarily of the mineral glauconite -- a potassium, iron, aluminum silicate. In some Delaware greensands, the glauconite content exceeds 90%. The remaining 10% is mainly quartz. In the past, greensand was used in Delaware as an inexpensive fertilizer. The only active greensand mine in the U.S. today is in New Jersey. Once mined, greensand is dried and used as a soil conditioner. Greensand is also used in water softeners primarily to remove iron from the water. Recent research has shown that greensand has the potential for use as a filter of heavy metals from industrial waste water and landfill leachates.

Sand and gravel are essential for supporting and maintaining economic development throughout Delaware. These natural resources are used primarily for aggregate in the productions of concrete for residential, commercial, and industrial buildings, bridge and highway construction, fill for road beds and foundations, water and wastewater treatment facilities, and for replenishment of our Atlantic and Delaware Bay beaches. There are relatively large quantities of sand and gravel in Delaware. Most of these resources occur as surficial or near-surface deposits that form a veneer of sand and gravel with a thickness up to 150-200 ft in the Delaware Coastal Plain. The deposits generally thicken from north to south across Delaware. However, the quantity and quality of the sand and gravel deposits is not evenly distributed throughout Delaware. There are significant quantities of sand deposits in Delaware Bay and off Delaware's Atlantic Coast that have been and will be used for beach replenishment (DGS Report of Investigations No. 63 An Evaluation of Sand Resources, Atlantic Offshore, Delaware).

The U.S. Geological Survey in cooperation with the Delaware Geological Survey compiles sand and gravel production information on an annual basis and reports it in U. S. Geological Survey publication entitled "The U.S. Geological Survey Minerals Yearbook, The Mineral Industry of Delaware." (http://minerals.usgs.gov/minerals/pubs/state/de.html). At this time, there are at least 11 major sand and gravel production operations in Delaware. General locations are shown on the map. The USGS reported that approximately 3.64 million tons of sand and gravel valued at about $24.7 million dollars were mined in Delaware in 2007. The DGS estimates that the quantities of sand and gravel produced from the State's natural resources are typically higher than those reported by the USGS. Reasons for this include: (1) not being certain that all major producers report production to the USGS; (2) state and local government agencies or companies that produce from borrow pits for their own use do not report production; (3) some operations that mine relatively small amounts of sand and gravel may not have been contacted, and, therefore, do not report production; and (4) production of sand from offshore areas for beach replenishment is not included in USGS figures. For example, according to the Delaware Department of Natural Resources and Environmental Control, in 2004 and 2005 approximately 4.4 million tons of sand with an estimated value of $20.3 million was dredged from the Delaware Bay and Atlantic Ocean and placed on beaches along the Delaware Bay and Atlantic Coast. For more general information related to sand and gravel production and use, the reader may refer to American Geological Institute Environmental Series No. 8 entitled "Aggregates and the Environment." This publication provides the general public, educators, and policy makers a better understanding of the aggregates and environmental concerns related to aggregate resources and supplies (http://www.agiweb.org/environment/publications/aggregate.pdf).