You are browsing the archive for quartz Archives - AGU Blogosphere.

31 July 2020

Friday fold: Two Mile Run Overlook

I spied an anticline last weekend while engaging in a day of solo geologizing along Skyline Drive in Shenandoah National Park. At Two Mile Run Overlook, I gazed west toward the southern tip of Massanutten Mountain, and noted what appeared to be an anticline in the Blue Ridge foothills: Annotated: And here it is in Google Maps,  with the perspective rotated to looking ~along strike to the north, and I …


15 July 2018

Chickie’s Rock, Pennsylvania

A virtual field trip to the deformed quartzites and metaconglomerates of Chickie’s Rock and Sam Lewis State Park in Lancaster County, Pennsylvania.


23 January 2018

A kid and his slicks

On a family hike, Callan’s son finds some interesting smooth lines on a rock. What are they? What do they tell us? Tune in for a brief history of Appalachian geology.


27 October 2017

Friday fold: Quantankerous veins

What does it mean for a vein to be “quantankerous?” Well, to start with, it’s quartz. Second, it has to be disagreeable or cantankerous. This vein, seen in meta-arkose of the Catoctin Formation near the summit of the Blue Ridge at Rockfish Gap (not Afton Mountain), is such a quantankerous individual: You’ll notice its “S” shape, which might imply top-to-the-left kinematics. But just down the outcrop is this set of …


16 May 2016

Trace fossils in the Massanutten Sandstone

Over the weekend, my wife and I took a walk with our son at the Storybrook Trail, an accessible trail with a fine overlook to the east over the Page Valley. There, the Massanutten Sandstone shows a bunch of big beefy trace fossils at this site: both bedding-parallel (Arthophycus-like) and bedding-perpendicular (Skolithos-like) traces. Here’s Bax on a photogenic slab of the quartz arenite, showing the inch-wide bioturbation: A short distance …


21 March 2016

Monday Geology Picture: Rose Quartz Lamp

This week’s “Monday Geology Picture” features a pretty pink rock lamp owned by some friends of mine. Many pink rock lamps are made out of salt crystals. However, this particular rock lamp is made out of a rose quartz crystal. The lamp is placed on top of a flat muscovite crystal.


18 January 2015

Geology Word of the Week: J is for Jasper

def. Jasper: A dense, opaque variety of chalcedony. Jasper is most often red in color but can also be yellow, brown, green, or gray.   For this week’s Geology Word of the Week post, we’re going to learn a little about silica, aka silicon dioxide or SiO2. More specifically, we’re going to learn about silica minerals. Silicon and oxygen are the two most common elements in the Earth’s crust and are found in many, …


16 December 2014

Buzzard Rocks

Back in 2011, when we were still living in D.C., Lily and I made a hiking trip out to Buzzard Rocks. It was a destination. Now that I live out here in the Fort Valley, I see Buzzard Rocks all the time, and I love it. It’s such a cool feature – a spot on the crest of the hill where you can see the slabby expression of steeply-dipping beds …


12 December 2014

Friday fold: Miette slate, Alberta

The Friday fold returns to Canada, looking at Neoproterozoic slate and quartzite at the southern terminus of the Icefields Parkway. Bonus features include ripple marks, graded beds, cross-bedding, cleavage, and boudinage.


17 April 2012

Strained Antietam Formation sandstone

I collected this sample the weekend before last on the Blue Ridge Thrust Fault field trip led by Alan Pitts. It’s a chunk of the Antietam Formation quartz sandstone, a Cambrian beach deposit. The face we photographed measures 15 cm by 12 cm. [gigapan id=”103122″] link It definitely looks best in full screen mode, so please feel encouraged to click through and explore it a bit. You’ll notice some great …


24 February 2012

Friday fold: Veach Gap anticline, in GigaPan

[gigapan id=”98833″] GigaPan by Alan Pitts, as part of the M.A.G.I.C. project that we are working on. Here’s another one from a few meters away. Here’s a shot from 2.5 minutes after Alan saw this anticline for the first time. Here’s some shots of my own early visit to the site, after I first found it.


26 May 2011

Fault in Massanutten Sandstone

Here’s a gigapan I shot last yesterday, looking west from “Blue Hole” towards a cliff of Massanutten Formation sandstone, south of Waterlick, Virginia. A prominent fault zone can be seen in the center of the image. [gigapan id=”78209″] Unfortunately, the auto-stitch deformed my face. I look like Quasimodo. Oh well. As usual, you can see it full screen, by clicking on the word “Gigapan” in the lower right. There, you …


24 August 2010

Tipping your tension gash

Tension gashes are small veins that open up when rocks get stretched. Often, they are arrayed en echelon with respect to other tension gashes, all oriented in the same direction. Here is a sample of tension gashes I found this summer in rip-rap (i.e., not in situ) at some building site in New England. (I forget where, but it doesn’t matter, since it’s rip-rap. Could have come from anywhere!) Check …