Diamond Hill (Ashaway Village), Ashaway, Hopkinton, Washington Co., Rhode Island, USA
|Latitude & Longitude (WGS84):||41° 25' 24'' North , 71° 47' 10'' West|
|Latitude & Longitude (decimal):||41.4233333333, -71.7861111111|
Quartz crystals were known here long before the large amethyst discovery.
|Neoproterozoic541 - 1000 Ma||Plainfield Formation|
Plainfield Formation - Pale-tan to gray, fine-grained quartzite, and pale- to medium-gray quartz-mica schist. Quartzite is massive to layered (bedded?). Includes Plainfield Formation and some rock mapped formerly as Blackstone Series.
Part of Hope Valley Subterrane
|Neoproterozoic541 - 1000 Ma||Neoproterozoic plutonic: undivided granitic rocks|
Plutonic: undivided granitic rocks
|Neoproterozoic541 - 1000 Ma||Neoproterozoic intrusive and metamorphic terranes|
Intrusive and metamorphic terranes
Mixtures of metamorphic and intrusive or plutonic rocks, tracts known as crystalline, migmatitic terranes, moderately to highly metamorphosed rocks of unknown origin with or without intrusions. This classification is inherently prone to variable interpretation, as other compilers might distinguish some packages by their metamorphic or gneissic protoliths, and the associated age ranges may be more variable.
References for regional geology:
Data provided by Macrostrat.org
Garrity, C.P., and Soller, D.R.,. Database of the Geologic Map of North America: adapted from the map by J.C. Reed, Jr. and others (2005). U.S. Geological Survey Data Series 424 .
USGS compilers. State geologic map data. State Maps.
Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d.
3 valid minerals.
- Rakovan, J., Mitcheltree, D.B., Benton, L., and Avella, S. (1995) Amethyst on milky quartz from Hopkinton, Rhode Island. Mineralogical Record 26:83-89.