rocks

Most of the specimens featured here, unless they are fossils

Geode Cake

a white layered cake with a blue candy geode decoration

Cake by Whisk Cake Company, http://www.whiskcakes.com

A talented baker made this geode layer cake with fondant for the layers and a rock candy geode surrounded by gold and silver leaf. I am very impressed with the banding in the geode. It looks very tasty. This cake was recently featured on Cake Wrecks in their Sunday Sweets section, which is a day of beautiful cakes to contrast with the awful cakes on other days. There are other geode and rock-related cakes including a malachite cake posted that day, so be sure to go to the Cake Wrecks post “Oh Em Geode” and see the rest.

Fairburn Agates

Special guest article from Show-Me Rockhounds club members Dan and Connie Snow

Fairburn agate fortification agate

Group picture of Fairburn agates – Dan Snow

Fairburn agates are a form of microcrystalline chalcedony, 100% silicon dioxide with a hardness of 6 ½ to 7 on the Mohs scale.  They are also called fortification agates because of their banding.  They were formed approximately 300 million years ago in an ancient limestone bed of an inland sea.  To hunt Fairburn agates requires looking at every rock and turning many with a rock pick.  It is strictly surface hunting no digging, mining, cracking or breaking rocks.   The photos shown are exactly the way the agates were found, with no cutting, polishing or tumbling having been done.

Fairburn agate fortification agate

Frog Rock – Dan Snow

Fairburn Agates found by Dan and Connie Snow. Collected from the Fairburn Agate beds of South Dakota and the Oglala National Grasslands in Nebraska.

Labradorite

Labradorite has become a popular gemstone because of the unique iridescent play of color that many specimens exhibit.  Labradorite is a feldspar mineral of the plagioclase series that is most often found in mafic igneous rocks such as basalt, gabbro and norite.  Some specimens of labradorite exhibit a Schiller effect, which is a strong play of iridescent blue, green, red, orange, and yellow colors as shown in the photographs above. The Schiller effect is also seen in fire agate and mother of pearl. Labradorite is so well known for these spectacular displays of color that the phenomenon is known as “labradorescence.” Specimens with the highest quality labradorescence are often selected for use as gemstones. Labradorescence is not a display of colors reflected from the surface of a specimen. Instead, light enters the stone, strikes a twinning surface within the stone, and reflects from it. The color seen by the observer is the color of light reflected from that twinning surface. Different twinning surfaces within the stone reflect different colors of light. Light reflecting from different twinning surfaces in various parts of the stone can give the stone a multi-colored appearance.

Source: http://geology.com/gemstones/labradorite/

Spring Forward to the Show

mineral clock with agates and apache tears

Photo by Stephanie Reed

We interrupt the Spring Gem and Mineral Show to remind you to set your clock forward one hour tonight for Daylight Savings Time.

This clock is from the collection of David Reed. It contains agates, Apache tears (obsidian), a craft store clock kit, and lots of resin. It looks pretty good with his other rock clock.

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

A Great Geology Book

Rocks and Fossils of the Central United States with Special Emphasis on the Greater Kansas City Area by Richard Gentile

The front cover of Richard Gentile's book, Rocks and Fossils of the Central United States with Special Emphasis on the Greater Kansas City Area

Front cover

The back cover of Richard Gentile's book, Rocks and Fossils of the Central United States with Special Emphasis on the Greater Kansas City Area

Back cover

Review by David Reed:

This book is great! It has beautiful pictures of the fossils that can be found in Kansas City and clear stratographic sections explaining the geology of the area. It also shows locations for picking up the fossils. Everything you might wish to know about Kansas City is in this book. Well worth the money and you can ONLY get it at UMKC (Amazon doesn’t have it). We purchased one when we visited the Sutton Museum.

Anthracite

Q: What makes rockhounds different from non-rockhounds?

A: They are happy to receive coal for Christmas.

Rockhounds love coal, and they love anthracite even more. Anthracite is a type of coal. It is very hard and burns slowly and cleanly due to its high carbon content and few impurities. It is rarer than bituminous coal (the soft, most common form of coal); in fact, less than 2% of the coal in the United States is anthracite. Also unlike bituminous coal, anthracite won’t leave soot on your fingers when you touch it.

There are four types of coal in all. The last two we haven’t covered yet are lignite coal and subbituminous coal, which have the lowest carbon content and are even softer then bituminous coal. Anthracite is the hardest and has the highest carbon content. Most of the coal in the United States is found in Colorado and Illinois, and is used primarily for making electricity and coke (coke is used by foundries to make iron and steel).

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