Thursday, April 7, 2016

A Worthy Addition to Your Science Library

Minerals of Georgia: Their Properties and Occurrences, by Robert B. Cook and Julian C. Gray is a worthy addition to the libraries of Geologists and Rockhounds alike.

Jose Santamaria, Executive Director of the Tellus Science Museum in Cartersville served as the editor of this new book. 

As a link-up to my new YouTube channel, I will be posting more book info here.

Wednesday, March 16, 2016

Future Plans

Plans are in the works for a YouTube channel "@geosciblog".  It's just a matter of sitting down in front of my little video camera, getting over "stage fright", and pushing that "on" button.

And the YouTube channel will be linked here to provide additional opportunities for science education.

It all starts with a dream and a "shoe string" budget.

I will be back to offer some planned subject titles.

Wednesday, February 17, 2016

A Spring Renewal

 For a variety of personal reasons (maybe to be discussed later - in part), my science blogging has been neglected for the past year.
I intend to change that.  That is why I posted this image of Trout Lilies, an early-Spring wildflower of the Georgia Piedmont and Blue Ridge.  These particular flowers were at Mt. Arabia in DeKalb County.  It took me three years of efforts to get this photo, due to missed flowering seasons and camera malfunctions.  When I finally got this photo, thankfully the ground was dry as I had to lay down to properly photograph these recumbent flowers.  Getting that flower photographed was on my "Bucket List".
Other plants on my Photo Bucket List include Wild Ginseng, Indian Squawroot, perhaps re-photographing Pink Lady Slipper and a few others, now that I have a better camera.
Anyway, the purpose of this blog is to impart information on science subjects and other subjects which may have subtle connections and learning opportunities that can be applied to the study of science.  In an effort to shake the "winter blues", I intend to be busier here.

Tuesday, February 16, 2016

Just an update...

Notice:  A significant number of posts (mid-2011 to early-March of 2015) have notations of "previously posted on such-and-such date", i.e., these were rescued from a now-retired blog of mine.  Here is given notice that unless the prior date is needed for pertinence, it will be retired from the titles - gradually.  This is being done to simplify the titles, not for any nefarious, fraudulent reasons. 

IOW, these were posted over a period of several years (2005 - 2008) on the other blog and I started copying/moving them to this newer blog.  I had put time and passion into these posts.  If any of them have now-disconnected internal links to the retired-blog, I will be fixing those, too.  Gradually.

Thank you for your time, visits, and thoughtful, constructive comments.

Friday, March 6, 2015

Geo-Tutorial I - A Brief Minerals & Rocks Primer

Student geologists generally study (and learn to identify) individual minerals first, before we learn to recognize them as components of rocks.

After we gain a working knowledge of minerals, we usually study igneous rocks second, as those are the original sources of most minerals.

Minerals are naturally occurring, inorganic compounds that are solid at normal atmospheric temperatures. They have orderly internal structures, defined characteristics, and a defined composition (or range of compositions due to ionic substitution), with a few exceptions.

Some minerals are elemental, i.e., the consist of a single element, e.g., diamond - but most are compounds consisting of one or more cations (positive ions) and one or more anions (negative ions).

We classify minerals by their anions, e.g., minerals related to pyrite (FeS2) are called sulfides, usually the anion is S or S2. These can include iron copper sulfides (chalcopyrite), silver sulfides, copper sulfides (cuprite), zinc sulfides (sphalerite), lead sulfide (galena). When sulfur is present in the formative stages of these minerals, whether in the original molten form, or in high-temperature, high-pressure mineralized water - called hydrothermal solutions, and if there are a variety of metals present, it is not unusual to find several different sulfide minerals together in the same ore body. This is the nature of the "massive sulfides" that were mined in the Ducktown, TN area and elsewhere.

The nature of the chemical bond between the cation(s) and the anion affect its chemical and physical and characteristics.

The four minerals in the rock above are all included in the Silicates class, wherein the anion consists of a silicon ion and three or four oxygen ions, which act as a single ion when bonded with a cation. Quartz is chemically an oxide (SiO2), but structurally, it is related to the other silicates. The vast majority of important "rock forming minerals" are silicates. Silicate-dominated igneous rocks range from the dense, iron-rich basalts found in Hawaii to the lighter, quartz/feldspar-rich granites that one sees at Yosemite National Park or Stone Mt., GA.

The term "rock" is a little less precise, as a rock is an aggregate of one or more minerals. We use texture (crystal sizes, mineral ratios, and overall composition) to classify igneous rocks. The rock pictured here is a piece of granitic igneous rock with a pegmatitic (large-crystals) texture and it contains four identifiable minerals. This particular specimen was collected along the Appalachian Trail on the north side of Springer Mt., GA. The biotite mica measures about 1-inch across, horizontally.

The presence of potassium feldspar and quartz identify the rock as granitic, while the relatively large crystal sizes identify the rock as being "pegmatitic". The large grain (or crystal) sizes of this rock are the key to this identification. Pegmatites are irregularly-shaped igneous bodies that fill fracture zones and because of the significant presence of pressurized water in the magma, larger crystals form (in a pegmatite in South Dakota, the lithium mineral Spodumene occurs in crystals 40 feet long). In a former pegmatite mine in Georgia, "books" of muscovite mica 5-feet across were mined.

In igneous rocks, the key to crystal size is the rate of cooling and the quantity of pressurized water. Molten lavas at the surface cool relatively quickly because of their exposure to the atmosphere, thus their crystals are generally small, if they are visible at all. If a lava contains some large crystals, these crystals were already solidified before the lava was erupted. Obsidian forms when a lava flow enters a lake, river, or the ocean and the lava is chilled. The ions are present, but there wasn't time for the mineral bonds to form, resulting in the formation of volcanic glass.

Molten magmas, below the surface solidify more slowly, resulting in larger crystals, especially when more water is present. The crystals of the Elberton Granite, northeast of Athens, GA generally measure 1 - 2 mm and the estimated cooling time for the granite to solidify was 1 million years (laboratory experiments with high-pressure furnaces provide some of this information). In a molten magma, there is a defined progression in which minerals crystallize, as the magma cools, different minerals solidify. The Bowen Reaction Series shows the temperature range in which certain major silicate minerals solidify. Quartz is the last major mineral to solidify and the first to melt. In the above sample, the order is biotite, potassium feldspar, muscovite, and quartz.

Generally, minerals that form as well-defined crystals do so because they have "room to grow", i.e., they are the earlier minerals to solidify in a magma (or lava) so they can grow within the remaining molten material or they have a cavity (a fracture, a gas-bubble, or other void) into which to grow. The later minerals solidify, the less room there is to allow crystal growth.

Thursday, March 5, 2015

A Few of My Favorite (Geology) Things - Part 1

My academic work and employment have covered a number of different branches of Geology.  This particular vignette falls within the science of Paleontology - the study of fossils. Studying fossils such as the Class Echinoidea (at left) can also extend into the study of layered rocks and the study of ancient ecosystems.

Echinoids compose a particular class within the Phylum Echinodermata.  Echinoderms, in broad sense include Asteroids (starfish), Crinoids (sea lillies, sea feathers), Echinoids (sand dollars, sea urchins), etc., and some extinct, weird critters such as Blastoids and Cystoids.

They are characterized by a pentameral symmetry, shown in the five "petals" of the fossil sand dollar at left. The echinoids are divided into Regular Echinoids (sea urchins, pencil urchins) and Irregular Echinoids (sand dollars, sea biscuits, sea cookies, and heart urchins). And they are one of my geo-hobbies".  I have been lucky enough to have had a couple of good collecting sites in my field mapping areas in SW Georgia.

The Regular Echinoids appeared in the fossil record during the Ordovician Period.  Generally the Paleozoic urchins are discovered as crushed specimens with some of their spines and plates present. Carefully cleaned and restored examples appear on eBay from time to time. Many of these types come from the Pennsylvanian shales in the Brownwood, TX area.  The Irregular Echinoids (heart urchins) began appearing in the fossil record during the Mesozoic Era, in the Jurassic Period.  The sand dollars began appearing in the fossil record during the latest part of the Cretaceous Period or early Tertiary Period.

The specimen above Periarchus pileussinensis is one that I collected from the Late Eocene Tivola  Limestone (approx. 40 million years old) in the old Medusa Cement Company quarry near Clinchfield, Houston County, Georgia, on the inner Coastal Plain. It was during one of my undergraduate field trips, probably in 1973 or 1974.  The Eocene Epoch (56 to 34 million years ago) of the Tertiary Period was a time of global warmth (palm trees in Alaska, crocodiles in the Dakotas), high sea levels, and great echinoid biodiversity.

Late Eocene sedimentary rock units on the Georgia Coastal Plain include the Clinchfield Sand, the Tivola Limestone, the Twiggs Clay, the Ocmulgee Formation, the Sandersville Limestone, and others, extending from south of Augusta southwestward to the Bainbridge, GA area. Much of the Florida Peninsula is underlain by Eocene limestones, such as the Ocala Limestone and in many surface exposures of the Ocala Limestone, echinoid collectors find their idea of heaven.

The Periarchus genus is found in North Carolina, Georgia, Alabama, Florida, and Mississippi and was present from the earliest Late Eocene until the end of the Eocene, when the genus, along with others, became extinct, perhaps due to the impact of the "Chesapeake Bolide".

In Georgia, the preceding species to P. pileussinensis was the Periarchus lyelli in the Clinchfield Sand (and elsewhere).  Also in Georgia, the next succeeding species in the lineage was Periarchus quinquefarius in the Sandersville Limestone.  Most of the Periarchus specimens found in Georgia measure about 3.5 to 4 inches in diameter, the size of the modern day Atlantic Coast sand dollars.   The smaller Protoscutella in the older Middle Eocene of the Carolinas, Alabama, and Mississippi may represent an ancestor to Periarchus, though most Protoscutella specimens are generally 1/2 to 1/3 the diameter of Periarchus.  To my knowledge, Protoscutella has not yet been found in Georgia (though I have tried).  And to my knowledge Protoscutella and Periarchus have not been found in the same layers.  When there are multiple fossil-bearing layers present in an area, Periarchus is always found in units younger than Protoscutella.

[Another time, I will post more photos of some of my Favorite Things.]