Post Date: Oct 15, 2011Trip Date: June 2010

Cone in Cone Structures a Geologic Mystery








Let me start this article by first stating, as a matter of fact, “Cone in Cone Structures” are not minerals. They are composed of minerals, which would place them in the category of “rock”. These structures are far more than just mere rocks however.

I realize this website is dedicated to minerals and I mean no disrespect with this article. What are rocks without minerals??? In an atmosphere of information, I feel this article is quite appropriate. And, I am sure after reading this article many of you will wish to find out more about these geologic mysteries.

What are Cone in Cone structures?






First and foremost......"these formations are not fossils". There is much speculation concerning what they are and how they were formed. I personally had never heard of these up until a few years ago when I read an article concerning the structures. With my curiosity at complete and full attention, I wanted to know more. I spent an enormous amount of time on the Internet and in my favorite library, the Carnegie Library of Pittsburgh. The Internet contains numerous websites dealing with information concerning these structures so please help yourself.

It seems the mystery lies in the fact that there has been numerous hypotheses proposed for over the past one hundred and fifty years trying to explain cone in cone structures. None of these have emerged as the most highly regarded. These structures remain a mystery to this very day.

Let’s talk about what is known of these structures to gain some insight into their nature. These structures were formed through a sedimentary process. As their names implies, cone shaped forms nest inside a cone shaped cup. They resemble fossils and are even mistaken for such, looking very similar to marine organisms. Here is a nice demonstration you can do at home. Or, you can use your imagination. Place or picture several ice cream cones sitting on a table with their points (bottoms) facing upwards. In amongst these ice cream cones place several additional cones with their points facing downward. Notice the cone angles fit together snugly and neatly. This is exactly the representation cone in cone structures suggest.

The debate has continued over just how these structures were formed. In the modern environment, no one has found these in the actual process of formation. Being unable to study the structures in a real-time setting has hampered all progress. The rocky structures are composed mainly of finely crystalline fibrous calcite,
calcareous material and clay. Some have been found to be composed of siliceous material. The structure has even been found in gypsum, siderite, and coal. Normally found standing vertically, the structures can be arranged in either thin beds or at the edges of large concretions. Some cones are quite small, less than an one inch tall while others can be upwards of 12 inches. Researchers have generally agreed on one thing. The structures form from the growth of calcareous fibers. And this is all they agree on. What they can’t agree on is when does the growth of calcareous fibers take place. Does it come before or after the rock has some rigidity? It all hinges on the rigidity of what will later become the rock.

I’ll list a few of the ideas being circulated as to their formation:

1. Induced pressure from burial
2. Expaning mineral growth while forming crystals
3. Inversion from aragonite to calcite
4. Growth of fibrous aragonite

From my understanding of the sources I have read, the one explanation readily being accepted is what is known as the “Displacive Crystal Growth Mechanism”. I will briefly attempt to relate this theory as I interpret it. The displacive crystal growth mechanism states when crystal formation begins in a partially consolidated sedimentary medium, as in cone in cone structures, the crystal structures begin to take up more and more space while in the process of formation. This process causes pressures to build up within the sedimentary medium. The resulting pressure build up, being uneven, causes the typical conical structure to form.

Cone in Cone Structures have been known since the late 1700’s. I located an online book source having a copy of “The Geological Magazine”. This particular copy was the January-December issue No.8, CCLIX-CCLXX, from 1886. On page 139 of this magazine, it detailed a correspondance between Mr. John Young and Professor Newberry discussing the formation of cone in cone structures. The list of sources for addition readings is quite long. And, I am certain should someone find these geological mysteries facinating you will seak out farther information. Here is a nice book, titled “The Nature and Origin of Cone in Cone Structure” by Bertram G. Woodland.


Cone in cone structures have been found in Pennsylvania, Kansas, West Virginia and other states, as well as other countries besides the United States.

I bring this non-mineral information to you simply because I do not merely collect minerals. I collect in several different categories. Some of you may also. My collection includes rock, rock oddities, ore minerals and specimens of the actual metal produced from these ores, core samples, core drilling holes, slags, UV materials, not so much the minerals but materials that fluorescent under UV and to a degree fossils just to mention a few.

My son who is eighteen years old now but started out when he was six has amassed a fine collection of metal objects from sites we visited such as: pipes, valves, ore cart light gauge rail, rail plates, hinges, nails, shaft roof bolts, machinery parts. If it’s metal and if he can carry it he collects it. His collection is something to see.

Should any of you out there collect related “stuff” I would like to hear from you.

I have been to the cone in cone collecting site, which I will now talk about, on three occasions. The site is located in the Erie, Pa. area, exact site not to be disclosed. The site is on private property and is not accessible to the public. I was allowed access to the property after a lengthy conversation with the property owner. My story will mainly be detailed through photos, which in themselves will tell the story.




















The collecting site is approx. a quarter of a mile long. Though, it can be longer I never explored it’s full potential. While on this property I agreed to collect samples and close the gate on my way out. That was it. The funny part of the story is that you can not actually access the collecting site itself. The cone in cone structures themselves must first fall out of the site before you can collect them.












The site where the structures are contained in, is an extremely steep sedimentary rock wall formation. It would be both careless and dangerous to even think of climbing this wall. Erosion and gravity have been working together for millions and millions of years and who am I to change things. All one has to do is have patience. Each of the three times I visited this site I was rewarded with numerous specimens. I have determined why I have been lucky enough each time to have collected the number of specimens as I have. First, these structures are not really known about. Someone finding one would most assuredly assume their find to be a fossil. The structures very closely resemble fossils. Most likely the only people who would know anything about these structures would be researchers. The structures are rock and most rock-collectors are not really rock-collectors but instead mineral-collectors. Once the structures tumble down the hill and into the creek they are at Mother Nature’s mercy. Having clay as one of their components causes them to erode very quickly. The swift moving creek pushes the structures along or pushes creek material over the structures grinding away at the soft rock. Their life expectancy is not long. The cones in cone structures are not really collectable items. They are not like having a beautiful crystallized specimen of tourmaline, aquamarine or amethyst. No, they are like having a specimen of shale or maybe sandstone. Not so glamorous. How many people do you know who has a cone in cone structure in their collections? I thought so. So there are several reasons, plus the fact the rock wall will not give up any samples until it’s ready.








One other condition at this site, beside the specimens being buried inside an unclimbable hillside is that at the bottom of that hillside, where the specimens can be found, is a major creek for that area. If and when the specimens are dislodged and gravity pulls them down, they tumble straight down into that creek. There are only certain times of the year when would it be feasible to visit there. This creek is normally very deep and the water is very swift moving.












My last trip to the site was in 2010. I was on a collecting trip at the request of a geologist friend of mine. I had mentioned to him two years earlier that I had gathered information concerning the structures and was setting out to collect cone in cone. He was welcomed to come along. At that time, he was not interested. After seeing several of the specimens he became as intrigued as I was with these odd structures. He had heard of and had seen photos of these but never saw the real thing. Now his interest was keen. And, in fact he asked if it would be possible to collect a few specimens for him the next time I went.

Adam and I were traveling to Ontario for our yearly Canadian rock trip. I wanted to give several specimens to rock friends in Ontario, Canada. We decided collect cone in cone two weeks before our Canadian trip.

I was happy to make a trip . I called the property owner to obtain permission and was granted it. Adam, a friend of mine and myself drove up to Erie for a day of collecting. Erie is about a two and a half hour drive from my house so this would be a day trip. I will include photos from a non-collecting trip also. It was late fall, the leaves had all fallen from the trees, I was in Erie and made a special stop just to take photos. The city of Erie sits on Lake Erie. Though the collecting site is not in the actual city limits.

Interesting enough, at this particular site, the formations are contained within "cyst" like assemblies. No, cyst is probably not a geological term. Looking at the photos however, one will understand my meaning. Numerous structures are found and therefore were formed together, as a distinct unit within a strata layer. Again, the number of sedimentary layers here indicate a lengthy period of time to have put down the number of individual layers. Notice the grouped formations reveal clearly visible individual strata layering. Dotted here and there are the cone formations. The cone formations do not comprise a strata layer of its own separate unique qualities.


























Collecting cone in cone structures from this locality requires nothing special. Chances are you are going to get wet so a change of clothes would come in handy but are not necessary. I usually take an extra pair of shoes and socks to change into. As far as tools, all you need is a big bucket or three, maybe a small pry bar and wrapping material like newspaper is fine.












Arriving at the site, the hillside is in plain view. We park and walk across a large open field. The creek is at the other end. Starting at the farthest end of the creek, we walk along the bank of this side for maybe half a mile hunting for specimens first. The cone in cone structures are heavy for their size so we usually pick out a spot or two and pile up any potential specimens as we go along. Carrying a bucket load of these is far to heavy. After scouting this side of the shore, we cross the creek and walk back up along a very narrow rock shelf just at water level. The creek itself rarely contains cone in cone structures due to the swift water current. The creek bed itself is pretty much solid bedrock, smooth and slippery. Large deep pools of crystal clear water flow down into Lake Erie itself. Most, if not all cone in cone structures will be found on the banks, in silt, sand and rock deposits. After searching, we return to our caches, sort through them to pick out the best ones and discard the rest. I always wrap any and all the specimens I collect, regardless of the site, to protect them from rubbing against each other and the bumps of transporting them home.

Normally when I visit any collecting site, I try to collect more specimens than are necessary. This habit offers me a larger pool from which to choose the best specimens. There is a big difference between collected samples and take home samples. I take a very limited number of the best specimens collected at that particular site. The remaining material is left behind, hopefully to be found by anoher collector. I would very much like to stress this point. A collection does not require you to remove ten buckets full of specimens from any one site. And, I have seen this happen. These type of collectors, in my opinion, are looters and pillagers with no concern for others except for their own greedy personal interests. Other than selling off the extras, how many specimens does a collection need???

Cone in Cone structures have a slippery "feel", like fine dirt between your fingers like that of a rosen bag or talc. They are "dirty" and will leave marks on your hands and clothing. Basically soft, they erode very easily. They will not tolerate much force should you attempt to shape them with a hammer and chisel nor will they accept much in the way of a side force such as prying them to remove them from the hillside. These structures are brittle, easily cracked and require gentle handling.










After collecting, we usually continue up to Lake Erie and Presque Isle for a Bar B Q on the beach and swimming for the remainder of the day.

I am added two late fall photos, as we were in the area, just to view the hillside without the leaves in the view.








Thank you and happy hunting

Franko