Long Articles

Spring 2017 Lectures

Lectures presented by the Association of Earth Science Clubs of Greater Kansas City

Friday, March 10, 2017

3:00 p.m. “Opal Down Under”, Ron Wooly, Owner of Dreaming Down Under

Saturday, March 11, 2017

1:00 p.m. “Earth Science… Facts, Frauds and Scams”, Mark Sherwood, Independence Gem and Mineral Society

2:00 p.m. “The Life and Hard Times of the KU T. rex”, Dr. David Burnham, Research Associate, University of Kansas, Lawrence, Kansas

3:00 p.m. “Medullary bone in Tyrannosaurs: a question of chickens, eggs and possibly more”, Dr. Josh Schmerge, University of Kansas, Lawrence, Kansas

4:00 p.m. “History of Gold Mining”, Doug Foster, Show-Me Gold, Missouri

Sunday, March 12, 2017

2:00 p.m. “The Life and Hard Times of the KU T-rex”, Dr. David Burnham, Research Associate, University of Kansas, Lawrence, Kansas

3:00 p.m. “Islands in the sun: Eocene fossil mammals from Turkey”, Dr. Chris Beard, University of Kansas, Lawrence, Kansas

Special Exhibits 2017

KANSAS CITY GEM SHOW SPRING 2017 FEATURE EXHIBIT

ROCK ART –Stone Quilt Design; Susan Judy; Denver, CO and WKP Accent Tables; Bill Peterson; Boulder, CO
Colorado artists Judy and Bill have brought some of their creations to the Kansas City Show.  Judy inlays natural materials in a stone mosaic to create pictures and Bill uses natural materials to create tables.

INVITATIONAL EXHIBITS (more…)

How Amethyst Cathedrals are Formed

purple amethyst cathedral in a museum with other minerals

Amethyst cathedral at the Sutton Museum. Photo by Stephanie Reed

Article by Dr. Bill Cordua, University of Wisconsin-River Falls

Have you ever been to a show and seen enormous amethyst geodes or crystals 3-5 feet or more in height? The tubular geodes are lined with deep purple gemmy amethyst crystals. How do such wonders form?

These excellent geodes come from a region along the Brazil-Uruguay border. The genesis of deposits on the Brazil side of the border has recently been extensively researched by an international team of geochemists lead by H. Albert Gilg of Techniche University Munchen in Germany (Gilg, et. al., 2003). The geodes are mined from several lava flows belonging to the Parana Continental Flood Basalt Province. This was one of the largest outpourings of basalt lava known. An estimated 800,000 cubic kilometers of lava extruded over an 11 million year time span. For comparison, this would be enough to cover Minnesota with a pile of basalt lava over 2 miles high. The lava outburst occurred as part of the opening of the South Atlantic Ocean during Cretaceous time about 130 million years ago. Of all these flows, however, only a few are known to host amethyst cathedral geodes.

Gilg et al. proposed a 2-stage model for their formation. In the first stage the large hollows form. This was caused as volcanic gases were released from certain lavas as they cooled. Not every lava has enough dissolved gas to form such big openings. As gas bubbles emerged from the congealing lava (much as bubbles emerge when beer or soda pop is poured) they coalesced as they rose. The lava was cooling fast too, and soon became so thick and sticky that bubbles quite rising and were trapped. The bulbous to tubular shapes thus point towards the top of the flow, a fact easily seen when the geodes are in place in the mines. These cavities, though, were empty of crystals.

The second stage was the formation of the amethyst, plus celadonite, calcite and gypsum fillings. An important clue to this event is the presence of small gas and liquid bubbles (called fluid inclusions) trapped within these minerals. These are samples of the mineral-forming liquids caught as the crystals grew. Fluid inclusions are treasure troves of information when studied with sophisticated instruments. Analyses of the fluid inclusions in the amethyst, calcite and gypsum show them to be filled with slightly salty water. This water had a temperature of no more than 100 degrees C, and possible less than 50 degrees C, during mineral formation. These cannot be fluids related to the magma that formed the lavas.

What was the source of these fluids? An amazing story unfolds from the radiometric dating of the minerals. The basalts formed about 130 million years ago, but the green celadonite, which makes up the rinds of the geodes, formed about 70 million years ago. For 60 million years these enormous cavities sat empty of crystals. Trace element data from the fluid inclusions gives another important clue to the source of the mineral-forming fluid. Below the lavas is a large aquifer (the Botucatu aquifer) filled with ground water that closely resembles the fluid inclusion liquids. Uplift and tilting of the area about 70 million years ago would force water out of the aquifer into the porous areas of the overlying lava. In the lava flow these waters would have found volcanic glass. Glass breaks down over geologic time and makes silica and other chemicals available in a form that is readily soluble in water soaking through the rocks. The water carried these chemicals into the cavities, where the amethyst and other minerals grew due to cooling and pressure release.

The special combination of geologic circumstances, unfolding over millions of years, is not often duplicated. Understanding the process gives geologist tools to prospect more efficiently for these wonders.

Reference:
Gilg, H. et. al, 2003, “Genesis of amethyst geodes in basaltic rocks of the Serra Geral Formation (Ametista do Sul, Rio Grande do Sul, Brazil): a fluid inclusion, REE, oxygen, carbon, and Sr isotope study on basalt, quartz and calcite” Mineralium Deposita vol. 38, p. 1009-1025.

The Glacial Drifter 08/2011, The Gemrock 06/2015

Weathering

Weathering is when rocks break down in place, that is, without moving the rock. This is usually done by water, but there are plenty of other physical and chemical processes that break down rocks without moving them. Physical weathering occurs when a tree root grows into a rock and breaks through, when a river cuts through a canyon, when particles carried by the wind abrade the rock, or during the process of frost wedging, which is when water fills a crack in a rock and freezes, then the ice expands and makes the crack deeper. Chemical weathering can be caused by acid rain or even regular rain, as minerals in the water weaken the rocks and make it easier for them to be eroded or broken later. Minerals can even react with chemicals in the air (such as iron and oxygen reacting to form rust, also known as iron oxide) or with other minerals nearby. Minerals are made of chemicals, after all, and there is nothing stopping them from reacting with one another.

There are a lot of interesting ways that minerals can change due to weathering, both physical and chemical. For example:

  • Limestone dissolves
  • Calcite dissolves
  • Gold may dissolve if manganese is present
  • Silver minerals can change to horn silver (cerargyrite) or dissolve
  • Feldspar changes to clay
  • Olivine and hornblende change to serpentine or chlorite
  • Pyrite changes to limonite and hematite
  • Rhodochrosite and rhodonite change to psilomelane or pyrolusite (manganese) minerals
  • Copper sulfide minerals change to malachite, azurite, cuprite, or metallic copper, or may dissolve entirely
  • Some copper minerals become partly limonite

Adapted from an article in Cycad, Flint Chips, Osage Hills Gems 11/1992

Characterization of Green Amber

silver ring with oval green amber

Green amber ring owned by Stephanie. It has nothing to do with this article. Photo by Stephanie Reed

David highly recommends this article on green amber from Gems & Gemology, 2009. Here is the abstract.

Ahmadjan Abduriyim, Hideaki Kimura, Yukihiro Yokoyama, Hiroyuki Nakazono, Masao Wakatsuki, Tadashi Shimizu, Masataka Tansho, and Shinobu Ohki

Abstract: A peridot-like bright greenish yellow to green gem material called “green amber” has recently appeared in the gem market. It is produced by treating natural resin (amber or copal) with heat and pressure in two stages in an autoclave. Differences in molecular structure between untreated amber and copal as compared to treated “green amber” were studied by FTIR and 13C NMR spectroscopy, using powdered samples. Regardless of the starting material, the FTIR spectrum of “green amber” showed an amber pattern but with a characteristic small absorption feature at 820 cm-1. Solid-state 13C NMR spectroscopy of the treated material indicated a significantly lower volatile component than in the untreated natural resin, evidence that the treatment can actually “artificially age” copal. A new absorption observed near 179 ppm in the NMR spectra of all the treated samples also separated them from their natural-color counterparts.

To read the whole article, go here http://www.gia.edu/gems-gemology/fall-2009-green-amber-abduriyim and click on “Download PDF”.

How To Clean Rocks

Household Products That Can Be Used As Rock Cleaners

by Betsy Martin
Safety: Always use plastic containers, rubber or nitrile gloves, eye protection, good ventilation, and great care when handling these products.
1. Zud or Barkeeper’s Friend cleansers (contains oxalic acid) – Warm or hot solutions will remove iron stains and are helpful with clay deposits. These cleaners can be used with a toothbrush on sturdy surfaces.
2. Toilet Cleaner (the hydrochloric acid type) dissolves calcite rapidly. After treating anything with an acid, rinse very carefully and soak in ample fresh or distilled water for a while to leach out any acid remaining in crystal seams and fractures. You can then follow up with a final soak in dilute Windex to neutralize remaining traces of acid.
3. Lime Away (dilute hydrochloric acid) dissolves calcite more slowly. Rinse as you would for other acid treatments (see above).
4. Calgon – Dissolve this powdered water softener in water. Use for clay removal.
5. Vinegar (Acetic acid), soda water, colas (carbonic and phosphoric acids) – Will slowly etch out very delicate fossils in limestone. Rinse as you would for other acids (see above)
6. Iron Out (iron stain and clay remover) – Mix with warm water and use with good ventilation. It will lose strength if stored. Rinse with plain water.
7. Bleach – Dilute solutions of bleach can remove organic deposits and disinfect minerals collected in areas used by livestock. Rinse with plain water.
8. Hydrogen peroxide – Use to remove manganese stains. Rinse with plain water.
9. Citric acid – Use to remove manganese stains. Rinse as above for acids.
10. Windex (with ammonia) – A good clay deposit remover and final surface cleanup. Works well in ultrasonic cleaners. Rinse with plain water.
11. Distilled Water – Use to clean sensitive species and as a final soak after acid treatment.

Removing Thin Coatings:
On moderately hard minerals – use toothpaste (a feldspar abrasive) and a toothbrush.
On hard minerals – use toothbrush with pumice powder and water.
On calcite (including bruised places) – quickly dip in vinegar or Lime Away and rinse thoroughly. Repeat. Soak in plain water afterwards to leach any acid from cracks.

The following tools can be used for cleaning minerals and tools:
Toothpicks, seam ripper, bamboo sticks, sewing needles in a pin vise, old dental tools, old toothbrushes, periodontal brushes, canned air, Exacto knife, single edge razor blades, cheap small stiff bristle brushes.
Source: The Gemrock, 06/2015

Chemical Composition of Gemstones

Here’s a neat infographic from Compound Interest (one of my favorite websites) that describes 16 different gemstones and why they have different colors. It also includes their chemical formulas and hardness on the Mohs scale.

Many gemstones would be colorless or a different color if not for the presence of small amounts of transition metals such as chromium or titanium. For example, you can see that aquamarine and emerald both have the same chemical formula Be3Al2(SiO3)6, but emeralds are green because of chromium ions replacing some of the aluminum ions and aquamarines are blue because of iron 2+ or 3+ ions replacing some of the aluminum ions. Click through to read the whole article, because there are many other ways that gems and minerals get their colors!

What color were the dinosaurs?

A dinosaur fossil of anchiomis huxleyi

Johan Lindgren/Sci. Rep.

In this article from Chemical & Engineering News, researchers use chemistry to find out what colors the dinosaurs were.

Researchers led by Johan Lindgren of Lund University, in Sweden, used a battery of analytical techniques to scrutinize the molecular makeup of a fossilized Anchiornis huxleyi specimen. This dinosaur is a distant relative of today’s birds, and its remnants were preserved for about 150 million years in what is now northeastern China.

The researchers’ thorough analyses have allowed them to conclude that some of the dinosaur’s melanin, or pigment molecules, and melanin-producing organelles have also survived the intervening epochs (Sci. Rep. 2015, DOI: 10.1038/srep13520).

Scientists have previously observed signs of similar biomaterials in fossils, but studies have lacked sufficient evidence to rule out the idea that these materials come from bacteria or other microbial intruders.

Using methods including infrared spectroscopy and time-of-flight secondary ion mass spectrometry, Lindgren and his colleagues have shown that the sample’s fossilized feathers contain substances that closely resemble modern animal—not bacterial—eumelanin, the pigments responsible for brown and black coloration.

Click here to read the whole article.

Angelwing Chalcedony

Article by special guest author David Reed

a long flowing wing-shaped rock appearing to be made of several small tubes, with red and blue colors.

From the collection of David Reed, photo by Stephanie Reed

This refers to a surface chalcedony formation characterized by groups of chalcedony filaments often intricately woven or connected together, so they resemble the feathers of a wing or flowing hair. They occur most often in the center of a vug or vein of agate, but can also occur in the center of a hollow thunderegg. These formations are usually found in Idaho or Oregon. It describes this type of surface chalcedony formation, regardless of whether the underlying formation is plume agate, tube agate, or moss agate. See below for several close-ups, all from the same specimen.

Close-up of red tube formations

Photo by Stephanie Reed

Close-up of blue and orange tubes

Photo by Stephanie Reed

Lots of chalcedony filaments all pointing the same way

Photo by Stephanie Reed

The tubes in Angelwing Chalcedony seem to follow the direction of flow of the silica-bearing fluid in air within the vug. They may form in similar fashion to the directional helictites (gypsum formations) in Lechugilla Cave (and elsewhere), or they may be directional helictites which were silicified.

Lechuguilla_Chandelier_Ballroom

Lechuguilla Chandelier Ballroom photo by Dave Bunnell

long squiggly white directional helictites

Directional Helictites Photo by Dave Bunnell

Although it looks similar, Angelwing Chalcedony is not the radiating tubes found in fossils of certain coral heads.  Angelwing Chalcedony was never alive, but the coral was. During mineralization, the form of the living coral was maintained, but the structure was changed from mostly calcite to mostly silica, and some of the voids were filled. The structure of the fossil is more regular; there was no irregular flow of fluid through a void, as there was with the Angelwing Chalcedony. The fossil specimen below was found eroding out of a Florida riverbed. It was purchased, to avoid diving with the alligators.

A round brown chunk of tiny tubes of coral with a white crust on the outside

From the collection of David Reed, photo by Stephanie Reed