Ron Schott's Geology Home Companion Blog

Concluding the geomeme of sand for this week… if you’re up to the challenge, comment on what you think the composition of the sand is and where it’s from. We’ll find out who knows their sand…

“Salt & Pepper” Sand (Macro)

“Salt & Pepper” Sand (15mm microscopic)

“Salt & Pepper” Sand (microscopic closeup)

*Not actual salt and pepper.

Continuing the geomeme of sand for this week… if you’re up to the challenge, comment on what you think the composition of the sand is and where it’s from. We’ll find out who knows their sand…

White Sand (Macro)

White Sand (15mm microscopic)

White Sand (microscopic closeup)

Continuing the geomeme of sand for this week*… if you’re up to the challenge, comment on what you think the composition of the sand is and where it’s from. We’ll find out who knows their sand…

Multicolored Sand (Macro)

Multicolored Sand (15mm microscopic)

Multicolored Sand (microscopic closeup)

*Although this post has Wednesday’s date on it, I’m actually posting it and the other “sand series” posts late Thursday evening.

Continuing the geomeme of sand for this week*… if you’re up to the challenge, comment on what you think the composition of the sand is and where it’s from. We’ll find out who knows their sand…

Green Sand (Macro)

Green Sand (15mm microscopic)

Green Sand (microscopic closeup)

*Although this post has Tuesday’s date on it, I’m actually posting it and the other “sand series” posts late Thursday evening.

It seems to be “Sand Week” in the geoblogosphere*. Ian Stimpson has been featuring deskcrops of local sandstones, and Brian Romans has reviewed Michael Welland’s new book Sand: The Neverending Story (which just went into my Amazon shopping cart) and conducted a Q&A with Michael over at Clastic Detritus (how apropos). Callan Bentley gets to host the roving virtual book tour next week, followed by David Williams and Andrew Alden. (Kansans don’t read books, I guess, or maybe it’s just that sand is still a bit of a sore subject here. Anyhow, I know when I’ve been told to pound sand.)

So for this week’s deskcrop series, let’s see how much the experts know about their sand. Four distinctive sands on Monday thru Thursday, and then an evil stumper on Friday. If you’re up to the challenge, comment on what you think the composition of the sand is and where it’s from. We’ll find out who knows their sand…

Black Sand (Macro)

Black Sand (15mm microscopic)

Black Sand (microscopic closeup)

*Although this post has Monday’s date on it, I’m actually posting it and the following four “sand series” posts late Thursday evening.

I’m loosening up the definition of “outcrop” today to feature some field shots of Quaternary geologic landforms. It’s not that I lack bedrock photos, but I want to include a little geomorphology while I’m taking you through my field expeditions.

Today we’ll gaze upon two lovely meander bends on the upper reaches of the Wind River, upstream of Dubois, Wyoming.

Meander Bends, Wind River, Wyoming

As pretty and educational as they are, there are even more river features to be seen in a wider GigaPan view from this vantage point…

.

It’s interesting that my most recent posts in the Deskcrop/Outcrop series have been getting more commentary on Facebook than here on my blog. I’d like to find a way to import those comments back here to the Wordpress blog, but I can’t seem to properly configure a Plugin to do the job. Harrumph!

I’m still playing catchup, so short writeups for the next few…

Today’s outcrop is a relatively local one. This escarpment in southwest Rooks County, Kansas is formed where a caprock of Tertiary Ogllala Formation conglomerate (of aquifer fame) unconformably overlies chalk beds of the Cretaceous Niobrara Formation (Smoky Hill Member). Elsewhere in western Kansas this same stratigraphic exposure is exposed with badlands topography developed in the chalk. But not here.

Ogallala Conglomerate Capping Niobrara Fm (Smoky Hill Member) Chalk, SW Rooks County, Kansas

The other interesting geologic feature at this locality was a beautiful set of raindrop impressions in the mudcracked Quaternary layers on the quarry floor.

Raindrops & Mudcracks

I believe I’m going to begin to use more Quaternary landforms for some of my upcoming outcrops…

I’ve fallen a bit behind in posting, but I’ll get caught up.

Today’s deskcrop was formed in the violent climactic (ultra?)plinian caldera-forming eruption of Mt. Mazama some 7700 years ago. It is a large pumice ball, with a diameter of almost a foot. I collected it from the forest floor just east of the boundary of Crater Lake National Park. As lightweight as it is, it’s still amazing to me to imagine the power of an eruption that could toss a fragment of rock this size such a distance from the vent. The entire region is covered by a blanket of ash and pumice fragments from this catastrophic eruption – it’s easy to recognize its buff color in roadcuts and borrow pits.

Mt. Mazama Pumice

Today’s deskcrop is a small piece of rhyolite with a bread crust texture. The bread crust texture forms as an extrusive rock cools, and resembles (wait for it)… bread crust. I have a much larger piece, somewhat more pumiceous, from the same locality, but I’ll save that one for another day.

Bread Crust-Textured Rhyolite

I usually do a quick Google search before I post each deskcrop, just to make sure my understanding of the samples I post about isn’t contradicted by other, possibly more knowledgeable folks who have published on the web before me. Normally that means checking the Wikipedia article (if one exists) for the rocks I’m posting about. It’s not uncommon that there are other reputable scientific accounts of the rocks I post about, as well. You can then, perhaps, imagine my disappointment when I got a look at the results of the search term “blue calcite“. I wanted to find a concise scientific explanation for its color causing mechanism, not how it affects my chakra when placed between purple candles. (Though I’m tempted to test whether it can actually “help keep teenagers away from bad influences or company”.)

[Update: A reader e-mailed me to point out this Caltech website that says, "Radiation is associated with blue and amber colors of calcite. Natural radiation interacts with sheared calcite to produce blue colors. An interesting experiment is to break a colorless calcite crystal into chips upto 3 mm in size. When some of the are chips are exposed to ionizing radiation (such as gamma-rays) they turn amber colored. If some more of the same chips are put into hydrolyic press and squeezed (One can use a KBr pellet press such as are used in chemisty laboratories and pressurize the die to the same pressure used to prepare KBr pellets), they will remain colorless. If they are subsequently exposed to ionizing radiation, they will turn blue." Unfortunately, no reference is cited on the website.]

Blue Calcite from the Valentine Mine, Adirondack Mts., New York

This blue calcite comes from the Valentine Mine, near Harrisville, NY in the Adirondack Mountains. This quarry also happens to be the site of my second cousin’s masters thesis (Hi Martha!). It’s a small world.