Share

First State Geology Newsletter Signup

First State Geology has been the newsletter of DGS for over 25 years.

Click here to signup!

Site content related to keyword: "Magnetite"

Baltimore Gneiss

Pbgn

Granitic gneiss with swirling leucosomes and irregular biotite-rich restite layers is the dominant lithology and constitutes approximately 75 to 80 percent of the exposed rocks. The remaining 20 to 25 percent comprises hornblende-biotite gneiss, amphibolite with or without pyroxene, and pegmatite. Granitic gneiss is composed of quartz, plagioclase, biotite, and microcline. Minor and accessory minerals are garnet, muscovite, magnetite, ilmenite, sphene, apatite, and zircon. The hornblende gneiss contains plagioclase, quartz, hornblende, and biotite with/without orthopyroxene. Accessory minerals are garnet, muscovite, clinozoisite, perthitic orthoclase, iron-titanium oxides, sphene, and apatite. Amphibolites are composed of subequal amounts of hornblende and plagioclase with minor quartz, biotite, clinopyroxene, and orthopyroxene.

Faulkland Gneiss

Ofg

Predominantly fine- to coarse-grained amphibolites and quartz amphibolites with minor felsic rocks, probably metavolcanic. Major minerals are amphibole and plagioclase with or without pyroxene and/or quartz. Amphibole may be hornblende, cummingtonite, gedrite, and/or anthophyllite. Halos of plagioclase and quartz around porphyroblasts of magnetite, orthopyroxene, and garnet are common features.

Brandywine Blue Gneiss

Obbg

Medium to coarse grained granulites and gneisses composed of plagioclase, quartz, orthopyroxene, clinopyroxene, brown-green hornblende, magnetite, and ilmenite. Mafic minerals vary from < 5-30 modal percent. A lineation due to a preferred orientation of quartz and mafic minerals is obvious on weathered surfaces. Unit contains thin, discontinuous fine-grained mafic layers.

B3 Marine Upper Cretaceous Formations of the Chesapeake and Delaware Canal

B3 Marine Upper Cretaceous Formations of the Chesapeake and Delaware Canal

In the Coastal Plain of Delaware, the non-marine Cretaceous sands and clays are separated from the Tertiary formations by a series of marine formations of Upper Cretaceous age. The sedimentary and hydrologic characteristics of these formations deserve detailed study because some of them are water-bearing beds. whereas others act as confining beds. A clear understanding of their relative age. and the presence or absence of unconformities is needed for proper correlation with formations found in wells throughout the State. as well as in Maryland and New Jersey.

Schenck rocks out on railroad geological tours

William S. Schenck of the Delaware Geological Survey prepares students for a rock excursion.

William S. Schenck, a scientist with the Delaware Geological Survey, has been taking students from A.I. duPont High School on Wilmington & Western Railroad tours, observing rock outcrop locations along the way.