The town of Winchester was incorporated in 1850; it was formed out of parts of Arlington, Medford, Cambridge, and Woburn.
Regions containing this locality
|North America Plate||Tectonic Plate|
Select Mineral List TypeStandard Detailed Strunz Dana Chemical Elements
Detailed Mineral List:
| ⓘ Babingtonite|
Reference: Harvard Museum of Natural History, no.91540; Yale Peabody Museum no. YPM6418
| ⓘ Sillimanite|
Reference: Yale Peabody Museum #2351
List of minerals arranged by Strunz 10th Edition classification
|Group 9 - Silicates|
List of minerals arranged by Dana 8th Edition classification
|Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O|
|Insular SiO4 Groups and O, OH, F, and H2O with cations in  and > coordination|
|Group 65 - INOSILICATES Single-Width,Unbranched Chains,(W=1)|
|Single-Width Unbranched Chains, W=1 with chains P=5|
List of minerals for each chemical element
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
251.902 - 541 Ma
|Paleozoic intrusive rocks|
Age: Phanerozoic (251.902 - 541 Ma)
Lithology: Intrusive igneous rocks
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
|Ediacaran - Cryogenian|
541 - 720 Ma
Age: Neoproterozoic (541 - 720 Ma)
Stratigraphic Name: Dedham Granite
Description: Gray granite to granodiorite more mafic than Zdgr north of Boston. Intrudes Zw, Zv. Extensive calc-alkaline plutons separated by Boston basin have long been mapped as Dedham. Those to the north of Boston and studied in this report, are referred to as Dedham North. Crystallization ages for the Dedham North suite (based on titanites and zircons) have been determined at 607+/-4 Ma, while ages for the Lynn are slightly younger at 596+/-3 Ma. Both are clearly part of the Late Proterozoic magmatic event. Dates on two samples from Sheffield Heights indicate that the diorite and granite are part of the Dedham North suite. The Dedham south and west of Boston has been dated at 630+/15 Ma (Zartman and Naylor, 1984). Dedham North Granite has a compositionally highly variable suite ranging from leucogranites to granodiorites, tonalites, and quartz diorite. The granites originated by partial melting of a sedimentary protolith, while the intermediate members show a mixing of granitic magma and mafic magma (Hepburn and others, 1993).
Comments: Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA018.Proterozoic Z age of Dedham is based on the following isotopic dates: 1. 630 +/-15 Ma by U/Pb methods on zircon (Zartman and Naylor, 1984) from Dedham Granite. 2. 595 +/-17 Ma by Rb/Sr whole rock methods (Kovach and others, 1977) from Dedham Granite north of Boston. 3. 640 +/-14 Ma by K/Ar methods on hornblende (Zartman and Naylor, 1984) per MA007. Original map source: Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon of Boston College in 1998; based on the 1983 USGS paper version (MA002).
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052.