Hematite Cone Page
My wife and I both got our geology degrees from what was West texas
State University in Canyon Texas, now WT A&M. Being close to
Palo Duro Canyon we spent a lot of time there.Geological and meteoric
processes have produced several interesting rock types in the
canyon. Near the top a band of opal is pretty easy to find
at the base of the Ogallalla. Most of the way down the canyon
slopes the Tecovis formation produces a lot of concretions, many
hollow. These geodes contain quartz crystals, calcite or
sometimes celestite. Other more rare minerals turn up
The most interesting rock in my opinion is the cone shaped concretions
forming in the upper Trujillo. These are hematite cemented
sandstone. They are distributed only very locally, requiring just
the right sedimentary, diagenetic, erosional, and now, meteoric
conditions. They are striking looking geochemical and geomorphic
products of the canyon worth some notice. These hematite cones
vary from a half-inch in size ot over three feet long.
Unfortunately, after three decades I have been unable to relocate those
larger than two feet in length. Many are about 6 inches as this one.
Some, such as this one
are perfect geometric cones. Large cones such as this one usually break to pieces on
weathering out. The angles of the cones varies from
about 10 degrees to about 80 degrees, presumabily dependent on the
vertical permiability of the sandstone. Internally they are
nested cone shaped hematite cemented zones within the parent sandstone,
such as seen here.
Some requirements for their occurance
1. Erosion of the overlying
Ogallalla and uppermost Trujillo sandstone.
2. Preferrably 50 yards or more of erosion back from the overlying
beds, presumably for many centuries of exposure to rainwater.
3.Presence of fine to medium
grained sandstone between the the first
Trujillo sandstone and the massive cliff forming Trujillo sandstones
for the cones to form in.
4. South facing exposure is
Timber Mesa and many other sites have no
cones on the north or east sides even when sandstone occurs in the
proper stratigraphic location.
5. Some loci for meteoric
iron precipitation. This is probably
weathering lignite and pyrite from plant fossils which are actually
preserved only rarely. Here
is a picture of fossil material from
the cone-bearing bed. Some of the fossil wood will burn when
heated with a match but the material is saturated with pyrite and
smells of sulphur when burned. Hematite-lined casts of the fossil
plants are sometimes present in the cone-bearing layer and often common
in beds below the cone-bearing sandstone.
I have been mapping and photographing these cones for the last several
years using a combined GIS and GPS method. Both air
photos and topo contours are very helpful in finding a suspected
Most sites are so rugged a planned route to the site must be loaded
a very long battery life GPS unit or the sites cannot be reached. Even
then more than three liters of drinking water are usually needed.
The cone occurance tends to be in remote very rugged sites so they
provide an excuse to hike in some very scenic places. So far I've
mapped them and their source beds at 1 meter accuracy from about ten
covering many square miles and have about a half dozen suspected sites
still to check.
Click here for a view of typical
Click here for a view of a "rhino
Click here for a distribution map for
one of the sites, Timber Mesa.
Click here to see what happens when
the source sandstone is too silty.
Click here to see how the cone
debris washes down from the source beds.
Click here for a scenic view along
Click here for a series of
views of embedded cones of different sizes
Click here for petrography
of the cones.
Click here for an
article on detailed 3D distribution at one site.(large and requires