BETA

Aquia Creek

Submitted by Raven Mueller on Thu, 2014-07-10 09:52
Trade Name Alias: 
Stone Type (Commercial): 
Availability: 
Unavailable
Physical Data
Munsell Color(s): 
Geology
Stone Type (Lithologic): 
Chronostratigraphy: 
Rock Unit: 
Grain Shape: 
Angular
Subangular
Grain Sorting: 
Moderately Well-Sorted
Grain Size: 
Medium
Petrographic Description: 

Specimen: 2014-050-1

This specimen is a sandstone. Detrital grains constitute 60 to 70 percent of slide area, void space ranges from approximately 15 to 20 percent, and the remaining area is occupied by fine grained matrix. This volume suggests the sandstone is composed of a relatively submature parent material. Of the detrital grains, quartz (poly and mono-crystalline) comprises about 65 percent of grains and feldspar 25 percent. Less common opaques occupy about 5 to 10 percent of slide area. A variety of mixed composition lithic grains (likely plutonic and metamorphic) and other miscellaneous minerals make up the remaining 10 to 15 percent. Based on these estimates this sandstone is classified as a lithic feldspathic greywacke. The constituent grains are moderately sorted. Quartz and feldspar grains are generally angular to subangular. Of the rarer minerals, several muscovite grains can be identified and one clinopyroxene. Feldspars show a variety of weathering states, with some grains predominantly transformed to alteration products such as sericite. Maximum grain size is .9 mm, and the minimum is .05 mm. The modal size range is from .2 to .5 mm. The matrix material is predominantly composed of a mica species with low birefringence. Distinct bedding is visible in the thin section by the presence or absence reddish brown of staining that emanates from ferruginous minerals such as the opaques, which are likely magnetite undergoing alteration. The bands likely reflect alternating oxidation conditions at the time the sedimentary deposits were formed. These same macro-structures are identifiable in hand section.
7/9/2015 MP

2014-050-2

This specimen is a sandstone. Sand sized particles constitute approximately 75 percent of slide area. Less than 1 percent of the slide area is void space and these pores may result from slide preparation. Matrix thus constitutes about 25 percent of slide area and indicates relatively immature parent sediment. The detrital grains are composed of approximately 50 percent quartz, 45 percent feldspar, 2 percent lithic grains 3 percent opaques, and less than 1 percent other identifiable minerals. These estimates indicate the specimen is a feldspathic greywacke. Maximum grain dimension is .75 mm and minimum is .05 mm. The modal range of grains is around .4 to .15 mm. Most grains are angular to subangular, which is consistent with an immature parent sediment. Feldspar grains show incipient stages of weathering with small patches of sericite formation up to 35 µm. Overall, though, weathering of grains is minimal, a clinopyroxene and several sand sized grains of muscovite show more advanced weathering but are still easily identifiable. The detrital grains appear to be overall moderately sorted. Matrix areas are composed primarily of micas; based on birefringence values kaolinite seems to be the most abundant with sericite and other micas also common. There is no macrostructure, such as bedding, visible in this thin section.
7/10/2015 MP

Images

Click thumbnail for larger image.
Specimen ID
2014-050-3 Image of specimen in dry conditions. Finish: Smooth sawndownload image Image of specimen in wet conditions. Finish: Smooth sawndownload image
2014-050-1 No image available.
2014-050-2 No image available.

Thin Sections

Click thumbnail for larger image.
Specimen ID Non-polarized Cross-polarized
2014-050-3 No image available.
2014-050-1 Specimen shown in non-polarized light.download image Specimen shown in cross-polarized light.download image
2014-050-2 Specimen shown in non-polarized light.download image Specimen shown in cross-polarized light.download image

Quarry

NOTE: Quarry locations are approximate.

Public Quarry at Government Island
Virginia
United States
38° 26' 53.9988" N, 77° 22' 59.9988" W
Virginia US

Report an Issue