Day #12 Deskcrop: The Hague Gneiss

I love the Adirondacks. As a kid my family spent a couple of summer vacations in Saranac Lake and then during my years in scouting summer camp at Floodwood Mountain Reservation hiking and canoeing the High Peaks Region was another highlight. Later, during my undergraduate years at Colgate University I made recreational trips to the Dacks and finally a series of geological field trips, including a couple of weeks on the OC (Colgate’s geology summer field camp). Even now I take every opportunity I can to pass through when vacation travel takes me back east. So it should come as no surprise that I’ll end up featuring quite a number of deskcrops and outcrops from that region. You’ve been warned…

Hague Gneiss

Today’s deskcrop is one that may be familiar to many geologists, because it is a distinctive metamorphic rock commonly found in collections such as Wards North American Rocks. The rock is the Hague Gneiss, an granulite grade metapelite, also known as a kinzigite. It’s mineralogy reflects its aluminous composition: prominent garnet porphyroblasts are common and readily visible in hand sample and sillimanite (+K feldspar) is commonly found in thin section. The rock is also justifiably famous for its lovely feldspar augen and gneissic fabric – in a structural geology class it might be used as an example of an augen gneiss.

Although it’s a weekday I’m throwing in a bonus outcrop macroGigaPan because, “it would be wrong not to.”


I’m glad to see even more deskcrops cropping up in the geoblogosphere. Remember you can review all of mine in Google Earth. Join the fun – there’s always room for more!

Day #11 Deskcrop: Belemnites

Fossilized bullets? Cigarette butts? Nope… belemnites.

In this case they’re Jurassic (~150 Ma) from the base of the Redwater member of the Stump Formation in the Red Wash area of Dinosaur National Monument, Utah.


And that’s about the sum total of my knowledge of these critters. If an enterprising paleontologist wants to elaborate they are invited to do so in the comments. :-)

Day #10 Outcrop: Kanouse Mountain Folds

Where NJ 23 passes through a gap in Kanouse-Copperas Mountain near the outlet of the Charlotteburg Reservoir, a spectacularly photogenic anticline-syncline pair is exposed in roadcuts.

Anticline – Syncline Pair

I also captured a 32 megapixel wider view of the roadcut – again, too big for Flickr or Picasa, and too small for GigaPan.

This past summer I revisited the spot with the hope of making a proper GigaPan, but unfortunately the best folds were too heavily vegetated to photograph, so I made due with GigaPanning the anticline in the highway median.


I’m glad to see that Ian Stimpson (Hypocentre) is also working on a Rock365 Project. His 10 day compilitation post got me thinking and I believe that the way I will aggregate my Deskcrop/Outcrop posts this year is via Google Earth:

Day #9 Outcrop: Anorthosite Highway Roadcut

IMG_8484From Tupper Lake to Saranac Lake in the Adirondacks of New York State runs NY 3, better known to geologists of the region as the “Anorthosite Highway”. There are some lovely pristine roadcuts through the Late Proterozoic Marcy Massif anorthosite, though many don’t offer a great deal of shoulder room to park your vehicle. Today’s featured outcrop is one of the more accessible roadcuts, located just east of Bartlett Carry.

Anorthosite Roadcut

In my pre-GigaPan days I was already experimenting with stitched panoramas. But what do you do with a 28 megapixel image? It’s too large to upload to Flickr and too small to upload to For now I host it on my own site.

Aligned Plagioclase Crystals

Although these rocks have experienced borderline amphibolite/granulite facies metamorphism, they largely retain their original igneous textures at this location. The plagioclase crystals that make up this anorthosite were probably concentrated by buoyancy (floating) in a dense ferrodioritic magma.

Up close, you can see the classic opalescence that is characteristic of some labradorite compositions…

Opalescence (or Labradorescence) in Plagioclase

And to take the chill off a cold winter’s night as I post this, here’s a reminder that summer is just a few score of blog posts away…

Black-Eyed Susan

Day #8 Deskcrop: Baraboo Rhyolite Doorstop (GigaPan)

IMG_7273Today’s deskcrop is actually my office doorstop. It’s a glacial erratic clast of Baraboo Rhyolite recovered from the Wisconsinan Terminal Moraine in the Keller Road Quarry, just south of the Badger Army Ammunition Plant near Prairie du Sac, Wisconsin. This was the first really successful GigaPan I shot in the macro format, as well. The GigaPan captures a cut face. The color is natural and not the result of any staining or postprocessing. If you zoom around you’ll find some remarkable zoned feldspar phenocrysts.

Baraboo Rhyolite MacroGigaPan
Launch Full Screen Viewer | Take Snapshots & Comment


Day #7 Deskcrop: Hawaiian Basalt on its Sixth Birthday

As I mentioned in this past Sunday’s Outcrop post I was on a field trip to the big island of Hawaii six years ago this week. After a miserable week of rainy weather, we finally got a two day break of glorious sunshine. By lucky coincidence we had planned exactly these two days to backpack out to Pu’u O’o in an effort to get up close to an active lava flow.

After a nine mile hike we hit the jackpot! We arrived at the west side of Pu’u O’o about an hour before sunset, just in time to find a gorgeous little flow front advancing from the Amalgamated Shield Complex onto 1983 vintage cinders. (Yes, we were on the island to party with the volcano on the eruption’s 21st birthday :-) .) The wind was gentle and at our backs as we approached the flows and a great experience was had by all.

Collecting Today's Deskcrop
Birth of a Deskcrop

There are plenty more stories and pictures from that trip, but today on its sixth birthday I wanted to feature the deskcrop that was born that day. Unfortunately it was impossible to bring back much more than pictures and memories from that experience, but a few of the pieces of basalt that were birthed on the tip of my hammer reside in a jar in my office to this day. Needless to say, they are the youngest rocks in my office.

Here they are:

The Hammer and Lava Fragments

Tip of the Spear (Hammer)

Happy Birthday, Deskcrop!

Happy Sixth Birthday Hawaiian Basalt Deskcrop!


“I love deadlines. I like the whooshing sound they make as they fly by.” — Douglas Adams

I was just getting settled into that post-holiday, pre-semester respite from responsibilities. You know, those days when you can go to sleep without setting an alarm. Those days that seem so wide open to do the things that you’ve really been wanting to do in your “copious free time”.

Alas, opportunity knocked on Monday and now I find myself right back into the thick of deadlines and prep work for the semester. It’s probably just as well – I’ve never seem to use those unstructured days as efficiently as I intend to. Nonetheless, there’s a real danger that if I don’t take a little time to review the past year and make changes for the coming one I’ll miss the opportunity presented by the dawning of the new year and slip right back into the bad habits of the old one. It’s not that I haven’t been thinking about resolutions for improving myself in the new year, but each day that passes without actions accelerates me down a slick and steepening slope. So this evening it’s time I addressed this blog.

Let’s face it, since posting my magnum opus “Building a Google Earth Geology Layer” last February, my blogging became increasingly sporadic and eventually all but dried up. It was not a blogging year to be proud of. Despite my aim to make that Google Earth Geology Layer a community effort I basically dropped the ball and tried to build the cathedral on my own, with predictable results. I aim to correct that this year, but it won’t happen overnight.

The first step to renovating my home in the geoblogosphere will be rededicating myself to producing my own posts. I’ve always been a sporadic poster, preferring to say something only when I had something original to say. I don’t intend to start recycling other people’s material for the sake of making more regular posts, but I am initially probably going to post more frequent, less developed posts than has been my norm. If this annoys some of my loyal readers I apologize in advance, and invite you to unsubscribe if necessary. Hopefully, once I’ve established a more regular posting pattern I will improve the quality of subsequent posts, as well.

One of the inspired ideas developed by my fellow geobloggers in a Google Wave was the idea of posting a deskcrop a day. I’m not above backdating a few posts to get myself kickstarted, just as I’ll probably schedule a couple of future posts once I get in the hang of things. I have an abundance of samples to post deskcrops each weekday and outcrops on the weekends and perhaps holidays (mirroring the way I tend to encounter rocks in my daily life), well into the new decade. (Would that it were outcrops on sunny days and deskcrops on days of inclement weather. Maybe someday…) You can rely on the fact that GigaPans will remain a common means of showing off some of my favorite samples.

There will be other changes, as well. I’ve been meaning to do a lot more with video on the web, for some time now – I certainly have the means, and it’s high time I started using it. I certainly hope to participate in more PodClasts, and I may begin to do more audio/podcasting on my own, in any case. GigaPans and Google Earth will increasingly be integrated into more coherent projects, if I achieve my goals for the year, and you can always count on me exploring the geological applications of new technologies (e.g. Google Wave, augmented reality, etc.). And there’s one more pot of stone soup stewing slowly on the back of the stove – when it’s ready you’ll all get a taste.

P.S. Apologies for the public navel gazing, but I reserve the right to do at least one of these each year.

Day #6 Deskcrop: Weathered Pyrite Nodules

The UPS delivery man dropped off a package at my office today, and he had a rock question for me to answer, as well. His friend had found a dense rock, nonmagnetic, with an odd pattern of clustered corners on the surface. Could it be a meteorite?

Sadly, no. But I had a deskcrop that fit that very description, collected in western Kansas, too. He agreed that this was indeed (most likely) what his friend had found.

Weathered Pyrite Nodules

It turns out that these pyrite intergrowths are not uncommon in the chalk beds of the Cretaceous Western Interior Seaway that crop out all around this part of western Kansas. They weather to a rusty brown (limonite/goethite?) on the surface, but maintain their intergrown cubic crystal forms. One of these days I’m going to try to clean the tarnish off of one of these and see if I can display the fools gold within.

Day #5 Deskcrop: Muscovite Book

Today’s deskcrop comes from the Dan Patch Pegmatite Mine Dump, located just west of Keystone and just north of Mount Rushmore in the Black Hills of South Dakota.

Muscovite and Quartz

Most of the muscovite at the dump is fairly weathered and flakes apart easily. However, some intact books can be found.

Note the Pseudohexagonal Crystal Form

This one displays a beautiful pseudohexagonal crystal form, but don’t be deceived – muscovite is monclinic!

The Hexagons Don’t Stack Vertically, However,
Making Muscovite a Member of the Monoclinic Crystal System

The Dan Patch Mine is owned by the Pacer Corporation of Custer, SD. Obtain permission before visiting or collecting.

Day #4 Deskcrop: Amethyst Crystals

I’ll start the week with the obligatory, purchased deskcrop of amethyst crystals. In this case, these were a gift from my parents a couple of years ago, and like many of my deskcrops they’ve seen double duty as a teaching specimen on occasion.

Amethyst Crystals

In nature stores and rock shops I’ve seen many samples like this (some much larger). They seem to often list a provenance as Brazil, though I’m not certain my sample ever included this information. Wikipedia tells me “amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks” and I have little reason to doubt just such an origin for this sample.


One thing I have often idly wondered about was the origin of the teal colored substrate on which the amethyst crystals are growing. It doesn’t appear to be unaltered basalt, though I could imagine that it is some sort of altered variety of that rock type. Any geologist want to take a stab at explaining the makeup of that teal material?