Welcome to Rock of the Month Club!
We are delighted to offer this space to explore geology and celebrate rocks. This page is an accompanying space to our monthly rock displays created and curated by local geologist Bob Stewart. As this is the inaugural display, Bob thought to begin with a rock present in abundance on Wellfleet beaches - Quartz! Read on for more information and to see our virtual display.  Be sure to stop by the library to see our exhibit of quartz and quartz-bearing rocks first hand.

QUARTZ

The Foundation of Wellfleet and Cape Cod

* Did you know –

1.Quartz makes up 90% of beach sand in Wellfleet and most of Cape Cod.

2. The hardness of quartz is 7 (Mohs hardness scale), greater than most other rocks and minerals on Cape Cod beaches, which is why it is so widespread.

3. Pleistocene glaciation created Cape Cod, and the outwash plains that make up Wellfleet and the outer Cape consist mainly of quartz sand. The outwash plains were deposited by braided streams of meltwater running off the glaciers.

4. The quartz-rich glacial deposits were derived from rocks from the Boston area, the Gulf of Maine, Maine itself, and northward.

5. All the specimens in this exhibit were transported to Wellfleet by glaciers, except the quarried specimen from Lantern Hill, CT.  Before it closed in the 1990s, the Lantern Hill quarry was a source of high-purity quartz that was crushed and sized for use as a filter sand in swimming pools and municipal water and wastewater treatment systems, among other uses.

Questions or comments?  Email Bob Stewart at iceagestewart@gmail.com

References:

Mineralogy and provenance of Pleistocene outwash-plain and modern beach sands of outer Cape Cod, Massachusetts, USA  Marine Geology Volume 130, Issues 1–2, February 1996, Pages 121-137

The Late Quaternary Construction of Cape Cod, Massachusetts: A Reconsideration of the W.M. Davis Model. 1996. Geological Society of America Special Paper.  Edited by Elazar Uchupi, G.S. Giese, D.G. Aubrey, and D.J. Kim.

Crosby, W. O. 1879.  On the Occurrence of Fossiliferous Boulders in the Drift of Truro on Cape Cod, Mass. Boston Society Natural History, Proceedings, Vol. 20, p. 136-140.

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