Rocks

Mini Field Trip July 2017

After our meeting on July 15, 2017 we decided to go on another mini field trip and look for fossils. There were crinoid stems, composita, and other fossils, as well as lots of blue shale. There was also something red and nobody knew what it was. I don’t have many pictures because it was very hot outside and my phone said something about battery temperature too high.

Composita fossils found in Kansas City. lots of crinoid stems and little fossils of many shapes

Composita found in Kansas City. Photo by Stephanie Reed

blue shale rocks in a row from kansas city mo

Blue shale. Photo by Stephanie Reed

bird in a tree

David met a friendly bird. Photo by David Reed.

man bending over gathering rocks outdoors

This is a traditional pose for members of rock clubs. Someday we may make a calendar. Photo by Stephanie Reed

Mozarkite Trip to Lincoln

MOZARKITE, MISSOURI’S STATE STONE by Roger K. Pabian

(Editor’s note: This article was written by Roger and printed in The Gemrock in 2002. It is written about a field trip taken by Roger and Bill and Betty White.)

On May 3, I took a trip to Kansas City and then on to Lincoln, Missouri, to examine the in place occurrence of Mozarkite, the Official State Gemstone of Missouri. As part of my ongoing study of cryptocrystalline and amorphous quartz family gemstones, I thought that the Mozarkite mine would be a worthwhile trip.

In Kansas City, I joined up with Bill and Betty White on Friday afternoon. Bill and I spent much of the afternoon at one of the major tool houses there and I purchased quite a few diamond tools and other tools that would be of use for stone and metal work. We also hit one of the retail salvage outlets, a store that carries distressed merchandise, as they often have many tools of considerable value for very low prices.

On Saturday morning about 7:00 A.M. we left Independence for the small town of Lincoln, Missouri. The town is famous for its annual rock swap in September. There we teamed up with Linville Harms, owner of the Mozarkite mine, and then went on to the mine. The attached photos of the Mozarkite and the Mozarkite mines help you get a better idea of what the site is like.

mozarkite

Photos by Roger K. Pabian

Mozarkite is not an accepted mineral name but is simply a trade name that was developed to promote the acceptance of the stone as Missouri’s official State Gem and to generate sales to both lapidary and tourists. The name has found acceptance in some circles but is not an acceptable mineral name in others.

Mozarkite has formed in place in marine sedimentary rocks of Ordovician age — it probably is most common in the Jefferson City Formation. The Jefferson City Formation is comprised mostly of dolomite with silty and cherty stringers running through it. There are very few fossils in dolomized rocks as the addition of magnesium to the calcium carbonate of the limestone usually results in complete re-crystallization of the rock and destruction of any fossils or sedimentary structures therein. We did observe a fragment of a brachiopod shell that escaped destruction. It appeared to be a flat-shelled, long-hinge lined form, probably a strophomenoid, but no other determination could be made of it. Much of the local lore about Mozarkite attributes it to igneous activity but there is no evidence for any in that area of Ordovician or younger rocks.

The Mozarkite appears to be of strictly marine sedimentary origin. Some of the nodules show evidence of an accumulation of siliceous gel or ooze on their outer surfaces.

There appears to be three different facies of Mozarkite. The gemmy kind is a dense, brittle form that shows no crystallinity at 10X magnification. A second kind is what the locals call “sugary” Mozarkite. Some of this is quite colorful and has interesting patterns and enjoys some gem use. The “sugary” kind, However, this does not polish nearly as well as the dense, brittle kind. Then, there are some nodules that appear to be very fine sandy textured.

The three facies or textures of Mozarkite suggest that sorting of particles may have been one of the key factors in the origin of the material. Sorting of particles simply means that as some energy form such as wind or flowing water moved a mixture of unconsolidated particles, the heaviest or largest particles are the first ones to drop out of suspension. You can observe this phenomenon on the gravel bars of a stream or in the bars along beaches, estuaries, or lagoons. The coarsest particles will be on the upstream end of the bar or nearer the bottom of the bar. It may well be that the gem Mozarkite is a quartz argillite, a sedimentary rock made up of quartz particles of clay size, that is, smaller than 1/256th of a millimeter. The gemmy facies could also be derived from silica of organic or volcanic origin. The “sugary” facies is made up of the particles larger than 1/16th but smaller than 1/4 mm.

The source for the silica that makes up Mozarkite is currently not known. It may have been from Precambrian granite rocks that are found to the south and east. Sponge spicules may have been the source of silica; I will not totally disregard them. However, I usually favored volcanic ash as the source of siliva for large bodies of chert or flint in marine sedimentary sequences. If there was any volcanic activity involved with Mozarkite, it was from volcanoes that were far away from the Mozarkite-bearing strata.

Mozarkite is a very interesting gem material that could shed a lot of light on the geologic events and processes that led to its formation. My comments above are only a few ideas about its occurrence. Like many other ideas on his stone, my hypotheses need more documentation before they can either be accepted or rejected. My hypotheses should probably read as follows: “Mozarkite is a quartz argillite of marine sedimentary origin that formed in situ in shallow seas of Ordovician age. The source of the quartz is shield rocks of Precambrian ages that lie to the southeast of the area from which it is not found.”

To prove that, several things need to be done. First, properly oriented (top and north) nodules need to be collected from in place in the mine pits. The nodules should not be examined in the field to avoid “high grading” the material. An outcrops map or diagram would need to be made that shows the places from which each nodule was taken. Similar sampling should be carried out from several different layers in several different parts of the mine. The facies of each nodule would need to be located on the map. Does one zone produce only sandy material whereas another produces only gemmy material? Or do these facies occur at random? Thin sections (30 microns) would have to be made. The nature of the particles (angular or rounded) and any cement between them would need to be noted. Is there a silica cement between the particles or does their angularity hold them together? Then other occurrences, both geographic and stratigraphic, of Mozarkite would have to be noted. The sedimentary structures in the Mozarkite and the host rock would also have to be observed and recorded.

By the time all of this is done, one has done enough work to earn a Master of Science Degree. As you see, there is no easy answer for Mozarkite. Perhaps, as a club, or group of clubs, we might think of funding a student to carry out the above kind of research.

mozarkite open pit mine Lincoln Sedalia

Linville Harms (left) of Sedalia, Missouri, and Bill & Betty White examine the open pit mine. Linville is the mine owner. Photo by Roger K. Pabian

 

1917 Geologic Maps

kansas city missouri geologic mapShow-Me Rockhounds member Dan Snow has provided these geologic maps of Kansas City from 1917 which contain topographical, geological, and cross-sectional data. The maps show where to find several different types of rocks common to this area. They are also a great way to see how Jackson County has changed in the last 100 years. The maps are in PDF format and are very high resolution, so please zoom in!

Cross Sections (21 MB)
Jackson County (55 MB)
Kansas City (53 MB)

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.

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).