Scalenohedral Form       Scalenohedral crystals occur in both generations of calcite but are less common from the 2nd generation.   Scalenohedrons from the 2nd generation have similar physical properties as the more complex crystals, but are generally much smaller.  The photo to the left displays a 2nd generation scalenohedron. 2nd generation scalenohedral calcite crystals on ferroan dolomite (specimen Joseph W. Vasichko) largest crystal measures 5 mm  West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio 1st generation crystals differ from the more complex crystals in several ways.  First, these crystals are always tan, yellow or brown.  Second, these crystals tend to form clusters as displayed in the photo to the right.  Also, 1st generation calcite is more likely to develop seams of small intergrown crystals, while seams of calcite created by the 2nd generation are often formed by a single large crystal which over grew its space.   Lastly, these 1st generation crystals have no reaction to ultraviolet light.

1st generation calcite on quartz (specimen Joseph W. Vasichko) crystal measures 7 mm  Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

BARITE BaSO4       A common misconception among Ohio collectors is that barite is a rare mineral throughout the state.  A more accurate statement is that barite is an uncommon mineral at most well known mineral localities in Ohio, with the exception of the Custar Stone company quarry.   The reason for this is that many of Ohio’s best known localities are Silurian age dolostones which generally do not produce the mineral.   Statewide, barite is frequently observed at Pennsylvanian and Devonian age localities including the Monroeville locality.   However, while barite is one of the more common minerals to occur in septaria at the Monroeville locality, it is perhaps the most difficult mineral to obtain in complete crystal form.   This is, in part, due to the tendency of the mineral to develop very large crystals.   Bladed barite crystals, typically unterminated, as large as 50 cm have been observed in these septaria.   Unfortunately, it is highly unlikely that a large bladed crystal on matrix would ever be collectable as this particular habit of barite is very brittle and unable to withstand the jarring force necessary to split open the septaria.   The typical result of using a sledge hammer to break the tenacious limestone is many small glass-like fragments of larger crystals spilling out of the opened pockets.    However, rare smaller but complete crystals of barite are obtainable by the patient collector.   The collector, willing to put forth the time and effort necessary to dissect several septaria, stands a fair chance of recovering a small but complete barite crystal.   These barite crystals are generally clear with internal feathering and may have vitreous or etched faces.  Thicker masses and large crystals may be gray, purple, yellow or rarely blue.

thin prismatic partially etched barite crystal (specimen Joseph W. Vasichko) crystal measures 2.3 cm x 1.6 cm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

barite crystal with calcite and aragonite on ferroan dolomite (specimen John D. Vasichko) specimen measures 7.7 cm x 5.6 cm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

Barite Occurrence      Barite is the second most common mineral, after ferroan dolomite, found in the limestone septaria at the Monroeville locality.  Veins of barite up to 5 centimeters thick, sandwiched between ferroan dolomite, can be seen on the surface of most unbroken septaria.   As these veins approach large pockets in the septaria the barite forms large bladed crystals.  Isolated smaller crystals resting on ferroan dolomite also occur, but are less common.  These smaller crystals are likely part of the same barite event, the only difference being the amount of the mineral emplaced.  The crystal form and habit are similar to the larger crystals, and the time of deposition appears simultaneous.   Although it is common to find barite over 2nd generation ferroan dolomite, all of the barite seems to have been deposited between the 4th and 5th generations of ferroan dolomite.   The reason for this is that pockets of 2nd generation ferroan dolomite are more common than pockets of 3rd or 4th generation ferroan dolomite.   No examples of 4th generation ferroan dolomite on barite have been found.  An excellent example of a complete isolated barite crystal on ferroan dolomite with calcite and aragonite is displayed in the photo to the left.   This crystal is quite large in comparison to most isolated crystals which are generally less than 2 centimeters in size.

Fig VI. forms of barite crystals.  A) thin prismatic.  B) basic  tabular form.  C) basic tabular form with macropinacoid and  brachypinacoid.  D) basic tabular form with macropinacoid,  brachypinacoid and second macrodome.

Barite Crystal Forms      Like celestine, a similar sulfate commonly found in Ohio, barite forms crystals in the normal class of the orthorhombic system.  In fact, some local collectors have mistaken the barite at the Monroeville locality for celestine because of the physical similarities of the two minerals and the fact that celestine is more common in the nearby Devonian and Silurian limestones and dolomites.  The barite crystals at this locality are generally tabular, although thin prismatic crystals as seen in the photo above have also been found.   An illustration of this crystal form is labeled A in figure VI to the left.  This crystal form employs 4 macrodome (d) faces, 4 brachydome (o) faces and 4 unit prism (m) faces.   The more common tabular crystals have 2 broad basal pinacoid (c) faces in addition to the faces found on the prismatic crystals, as illustrated by crystal B.   However, the basic form is infrequently observed at the Monroeville site.   More commonly, barite crystals will have an additional 2 macropinacoid (a) faces and/or 2 brachypinacoid (b) faces.   A crystal with both of these pinacoid faces is illustrated as crystal C.  Rarely crystals will have multiple sets of 4 macrodome faces.   These faces are generally thin and exist on either side of the macrodome (d) faces.  Crystal D is an illustration of a crystal with a second set of macrodome faces.  Crystals with up to 3 sets of macrodome faces have been observed at this locality.

water clear tabular barite crystal on ferroan dolomite (specimen Joseph W. Vasichko) crystal measures 1.3 cm  West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio barite crystal with crystalline bubble inclusions (specimen Joseph W. Vasichko) crystal measures 8 mm  West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

Barite Crystal Development      At the Monroeville locality, barite has a unique morphology, which often causes the crystals to have a mix of vitreous and crude faces.  Discounting the fact that some crystals of barite have been heavily corroded from exposure to the elements of the river, many of the fresher crystals on the inside of septaria have certain naturally rough faces.   These rough, rounded, etched or feathered faces make the task of identifying additional modifications nearly impossible.   A very few sporadic crystals without distorted faces have also been observed but are not as common.  The crude faces are generally an indication of the rate at which the crystals formed, and furthermore that some faces likely grew too quickly to fully develop.   While the basal pinacoid, macrodome, brachydome and macropinacoid faces are usually sharp with a glass-like polish, other faces like the unit prism and brachypinacoid faces are more often rough and uneven.  Occasionally the macropinacoid will also be rough as well as any additional macrodome faces.  A typical example of this phenomenon is displayed in the photo to the left.  Notice how the unit prism has unique stress mark edges as if this face was stretched away from the surrounding sharper faces.  The center of this face is smooth, but does not have the glass like polish found on many other faces of this crystal.   This is very characteristic of the unit prism faces and may indicate that the unit prism formed slightly too fast.   The macropinacoid and brachypinacoid are often much rougher, almost to the point of being unidentifiable.  These faces likely developed at an even faster rate.  Another example of this development can be seen in the crystal in the photo to the lower left.  This crystal has 3 sets of macrodome faces.  Notice that the main macrodome is sharp and the succeeding macrodome faces are increasingly crude.   This effect is often amplified in very large crystals, causing  the macropinacoid and/or brachypinacoid to have feathered faces.  Crystals larger than 2 centimeters in size are also more opaque with multiple growth faces and are less distinct than crystals of smaller size.  An example of this is pictured to the lower right   Larger crystals are of the same form as the small isolated crystals, but are merely elongate along the Y axis of the crystal.  Smaller crystals are typically water clear with well defined faces and unique crystalline shaped bubble inclusions.  These are viewable inside the crystal in the photo to the lower left.   Most barite will have these inclusions, but smaller crystals tend to display this characteristic best. barite with quartz on ferroan dolomite (specimen Joseph W. Vasichko) crystal measures 2.7 cm  Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

bladed, etched barite intergrown with ferroan dolomite (specimen Joseph W. Vasichko) specimen measures 5.8 cm x 4.6 cm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

Physical Properties of Massive Barite      In addition to the difference in color and clarity, large crystalline masses of barite from the septaria have a few other unique characteristics, rarely observed among small isolated crystals.  First, while these masses are often  created by multigrowth parallel or bifurcated crystals that over grew the pockets, smaller crystals tend to be singular individuals.  Second, the larger crystals and masses are often opaque with patches of pale yellow, purple, gray and rarely blue color.  The specimen in the photo to the left is an example of pale purple massive crystalline barite.  Large masses occasionally show a medium salmon red fluorescence under short wave ultraviolet light as displayed in the photo to the right.  The fluorescent yellow mineral is massive ferroan dolomite. barite on ferroan dolomite under SW UV (specimen Joseph W. Vasichko) specimen measures 7.3 cm x 4.9 cm Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

aragonite sprays on quartz and ferroan dolomite (specimen Joseph W. Vasichko) field of view is 4 mm x 2.5 mm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

ARAGONITE CaCO3        Radiating, fibrous sprays and crusts of snow white to cream colored aragonite are regularly found at the Monroeville locality.  While individual crystals up to 3 millimeters have been observed, aragonite crystals are more commonly less than .5 millimeters in size.  Often, but not always, the aragonite is found in association with and grown over partially dissolved calcite on later generations of ferroan dolomite.  This may indicate that the development of the aragonite was made possible by the presence of calcite.  Although these typically occur as extremely small, micro crystal clusters, the mineral’s presence is worth mention as this polymorph of calcite is rarely observed in the state.  It should be noted that aragonite is regularly encountered at other Devonian age septaria occurrences in Ohio as well.  However, these constitute a very low percentage of the total number of mineral localities in the state.  An example of micro aragonite sprays on ferroan dolomite and quartz is displayed in the photo to the left.  The fact that the ferroan dolomite crystals are slightly translucent indicates the minute size of the crystals in the photo.  Aragonite from this locality also has a pale blue white fluorescence under all wavelengths of ultraviolet light.  Crystals associated with partially dissolved calcite are more abundant and fluoresce brighter than isolated sprays.

SPHALERITE (Zn,Fe)S         One of the most highly sought sulfide species by Ohio mineral collectors is sphalerite.   Sphalerite has greater appeal to most serious Ohio collectors than pyrite and marcasite and is more frequently encountered, and therefore more obtainable, than other sulfide minerals such as galena.  Commonly, Ohio sphalerite specimens consist of sharp wine red, orange or black crystals on limestone or dolostone matrix which with few exceptions are of identical form and cannot be differentiated by locality.  At the Monroeville locality, rare examples of crude, rounded, multigrowth brown to black crystals up to 2 centimeters on ferroan dolomite have been  Sphalerite on ferroan dolomite (specimen Joseph W. Vasichko) crystal measures 5 mm  Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio observed.   These crystals, though less distinct than sphalerite crystals from most Ohio limestone and dolostone quarries, are more unique.   The sphalerite was deposited some time after the 4th generation of ferroan dolomite, though its exact place in the sequence cannot be pinpointed.  It should be noted that most septaria will not produce sphalerite and those few which do may have only one or two isolated crystals.  It is likely that sphalerite crystals may occur differently than those in the photos to the left and right, as an insufficient number of examples have been recovered to make any broader generalizations.

sphalerite cluster on ferroan dolomite (specimen John D. Vasichko) specimen measures 5.3 cm x 4.3 cm  West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

whewellite on calcite and ferroan dolomite (specimen Joseph W. Vasichko) mass measures 3.2 cm x 1.6 cm Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

WHEWELLITE Ca[C2O4]+ H2O     Thin seams, milky white masses and crude, often partially dissolved, crystals of whewellite are rarely found at the Monroeville locality.  This substance is more commonly found in septaria a few kilometers to the north along the Huron River near Milan in Erie County.   Mineral collectors disagree on the validity of whewellite as a true mineral species, as the substance has organic components in its formula.  The mineral purist would completely discount whewellite because of the organic connection.   In fact, whewellite is known to form quite rapidly on decaying saguaro cactus and agave plants in Arizona.  It is also the chief component of kidney stones.  In these instances, the compound would be better described as a bio-mineral, because of the non-geological development.  However, the compound has also been reported in hydrothermal veins, where living matter is not present.  In this situation, it is more likely a true mineral because it is formed with no biological connection and has a set chemical formula.  At the Monroeville locality, whewellite is directly linked with biological matter, namely fossilized arthrodire bones.  Although the substance precipitated in a geological environment, its origin stems from organic matter and therefore classifying it as a valid mineral is not entirely correct.  Legitimacy aside, at best this locality yields unappealing specimens of whewellite.

MARCASITE FeS2       Small brassy blades, needles and numerous other crystal forms of marcasite are commonly found on ferroan dolomite in association with quartz, calcite and barite.  It is impossible to precisely pinpoint the individual positions of marcasite in the sequence as there are perhaps tens of generations.   It may be possible that the marcasite is continually forming, though some habits appear to be more prevalent at particular stages in the sequence.   Some of the largest marcasite crystals found in the septaria are long needles, which have been observed up to 2 centimeters in length.   The longest needles have been found protected inside crystalline quartz.  These crystals have a thick base which elongates into a slender needle termination.   An example of this can be viewed in the photo to the upper right.   Notice that this particular marcasite needle was formed after the chalcedony generation, and later encased with 3rd generation quartz crystals.   Smaller crystals of similar form, not encased in quartz have also been observed.   Free standing crystals of equal size may exist, but are either too fragile to withstand the collecting method or have been dissolved.   One of the more interesting marcasite habits are feather like blades which occur more frequently on early generations of ferroan dolomite.  Typically these are micro sized crystals up to 4 millimeters in length, 1millimeter in width and immeasurable thickness.  These crystals attach to the matrix at the narrowest width of the blade and expand slightly towards the termination.  The sides of the blades are of unequal length with an angular termination as seen in the photo to the lower left.  When viewed under  marcasite blade on ferroan dolomite (specimen Joseph W. Vasichko) crystal measures 1.5 mm  Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio magnification, these blades are highly iridescent.   An entire study could be devoted to the variety of other less common forms observed at the Monroeville locality.   Most of these appear more frequently on later generations of ferroan dolomite.  Marcasite forms which have been identified include tabular, pyramidal and prismatic, each with various modifications.  In general, these are less than 1 millimeter in size. The photo to the lower right exhibits typical tabular marcasite crystals on ferroan dolomite.

marcasite needle on chalcedony inside 3rd generation quartz (specimen Joseph W. Vasichko) needle measures 1.1 mm in length West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio marcasite crystals on ferroan dolomite (specimen Joseph W. Vasichko) field of view is 2 mm x 1.3 mm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio

PYRITE FeS2       The more common iron sulfide polymorph found at the Monroeville locality is pyrite.  Pyrite is found abundantly at the locality as micro crystals and crusts inside large septaria and as crystalline nodules throughout the shale.   Some of the septaria also have a rind of solid pyrite.  Like marcasite, pyrite appears to have formed at several positions in the sequence.  The majority of pyrite crystals found resting on ferroan dolomite and other vein minerals inside the septaria are less than .5 millimeters in size.  Several crystal forms have been observed, but the majority of crystals are predominately cubic or octahedral with various other modifications.  The photo to the right shows a typical example of pyrite crystals on ferroan dolomite.   Large nodules and discoidal masses of crystalline pyrite, many with projecting pseudomorphs of marcasite, are abundant at certain levels  pyrite nodules from shale (left 7.7 cm x 5.3 cm), (right 4.8 cm x 4.6 cm) Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio of the shale.  Pyrite nodules up to 50 centimeters have been observed and can be found littered at the base of some shale cliffs.  Most of the pyrite nodules have veins of barite, calcite or  ferroan dolomite.  Examples of pyrite nodules from this locality are exhibited in the photo to the left.  Similar pyrite nodules are found throughout the Ohio shale, most notably near Frankfort in Ross County

pyrite crystals on ferroan dolomite (specimen Joseph W. Vasichko) field of view is 8mm x 5 mm West branch of the Huron River at Lamereaux road bridge Monroeville, Huron Co., Ohio