Ohio Collector's Series       v.1   art.5
Mineral Habits of
the C.E. Duff and Son Inc. Quarry

Logan County, Ohio

by Joseph W. Vasichko


 
Introduction
     At one time, the C.E. Duff and Son Inc. quarry near Huntsville, Ohio was one of the most heavily collected localities in the state of Ohio.  Most knowledgeable mineral collectors recognize the Duff quarry as being famous for one mineral, Pyrite.  This locality has been noted for producing world class specimens of the species in a multitude of crystal forms.   In fact, many would argue this to be one of the best world-wide localities for observing Pyrite crystal forms.  For more than 30 years, Pyrite crystals from this locality have been a source of study for mineralogists and have been well documented and described on countless occasions.   Over the years, high quality specimens of Pyrite and other minerals were abundant and easily collected in the Southwest portion of the quarry.  The shallow depth of the quarry and the uniformly horizontal bedding of the dolomite lended to a relatively safe collecting atmosphere.   In recent years, the operation has taken a new direction, opening a deeper, mostly unmineralized, second level.  In addition, quarrying on the upper level has generally proceeded to the Northeast, away from the best mineralized zone into an area predominantly free of mineralization.  The combination of these factors caused recent collecting to be somewhat, but not completely, unproductive.  Unfortunately, liability concerns, in this increasingly litigious age, have closed the door to current mineral collecting. 

Pyrite and Dolomite on Dolostone
(specimen John D. Vasichko)
specimen measures 7.1 cm x 4.3 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio

 
History
     C.E. Duff and Son Inc. was founded in 1955, although aggregate mining around Huntsville can be traced back to the late 19th century.  The current two level operation, owned by James E. Duff, is on the East side of State Route 117 just North of Huntsville, in Logan County.  An earlier quarry, once owned by the Western Ohio Stone Co. and later by C.E. Duff and son Inc., was directly opposite the new operation and is now completely flooded.  Both quarries offered collectors with the same basic mineralization.  Other than historical reference, little, if any, differentiation can be made between the minerals found in the older and newer quarries.  The original quarry was much smaller than the current operation.  The general offices for C.E. Duff and Son Inc., located in front of the current quarry, are unmistakably marked by 2 large arches from the 1964 New York World's Fair.  C.E. Duff and Son Inc. also operates another limestone quarry near Kenton, in Hardin County, and several sand and gravel operations in the Bellefontaine area.  The company also owns and operates a number of Ohio Ready Mix Inc. plants in conjunction with the aggregate quarries.  Several sons also operate related business near the Huntsville quarry.


Duff Quarry Sign-- Arches from the 1964 New York World's Fair
C.E. Duff and Son Inc.
Huntsville, Logan Co., Ohio

 

Blast pile on the upper level 
C.E. Duff and Son Quarry
Huntsville, Logan Co. Ohio
Geology
    The dolomitic limestone, or dolostone, being mined at the C.E. Duff and Son Inc. Quarry in Logan County is of upper Silurian age and is recognized as a member of the Salina group.   However, many parallels can be observed in the geologic features of this strata and the rocks in the Bluffton Stone Co. Quarry in Allen County, including raindrops, distinctive mudcracks and stromatolites.   These similarities lead to the conclusion that this dolostone is likely part of the Tymochtee formation.  This strata lies just below the Columbus Limestone of Devonian age.  Similar rocks and mineralization habits have also been observed in nearby operations including the quarry at Northwood, also in Logan County, and the quarry at York Center in Union County.   The material being quarried on the upper level is generally bluish gray in color and shale-like, ideal for flagstone.   Due to the high levels of Iron in the strata, some of the thinner layers of the Dolomite are red in color.  The lower level of the quarry houses a more dense and siliceous brownish gray material which is suitable for aggregate needs.   Stone from this part of the quarry is typically void of mineralization or noticeable geologic features.

 
Mineralogy
    Although slight to moderate mineralization is evident throughout the C.E. Duff and Son Inc. quarry, commonly known to mineral collectors as "Duff's", the most aesthetic mineral specimens are generally found at the South end of the upper level.  For the most part, mineralization occurs as crystals and crystalline masses lining or filling small pockets and crevices parallel to the bedding plane.  On average, most pockets range from 1 centimeter to 8 centimeters in size, but occasional larger pockets up to 25 centimeters have been observed.  In the most productive areas, pockets are clustered together and typically have similar mineralogy.  Often these pockets form in algal molds, stromatolites or under and along stylolites.  Anhydrite nodules may also be responsible for some of the pockets at this locality.  Rare Anhydrite and Gypsum nodules have occasionally been observed.  The C.E. Duff and Son Inc. quarry is generally considered to be near the boundary of the Findlay Arch Mineral District.   This District is determined by the presence of brown Fluorite.  Occasional brown Fluorite has been observed in various parts of the Quarry.  Well formed brown, yellow, clear and purple Fluorite crystals are extremely rare and highly sought after from this classic locality.  The most common minerals found at the Duff quarry are Pyrite and Dolomite.  Infrequent crystal specimens of Sphalerite and Calcite are also occasionally encountered throughout the quarry, although massive Calcite fillings are somewhat common.   Some pockets also contain moderate to heavy amounts of Asphalt. 

Pyrite pocket formed under stylolite
C.E. Duff and Son Quarry
Huntsville, Logan Co. Ohio

 
Pyrite FeS2
    Without doubt, the C.E. Duff and Son Inc. quarry is the premier Ohio locality for Pyrite.  While much larger crystalline Pyrite concretions are relatively abundant throughout the Devonian age Ohio Shale, quality specimens from this quarry are, in general, more aesthetic and in much higher demand.   At this classic locality, this relatively common sulfide mineral is known to develop numerous distinct crystal forms, often in association with Dolomite, Calcite and rarely Fluorite.  Although many of the quarries in the Findlay arch mineral district occasionally produce specimens of the species, no other quarry in Ohio is noted for producing the abundance of good Pyrite specimens which the Duff quarry has turned out over the years.  The average Pyrite crystal from the C.E. Duff and Son Inc. quarry is quite small and well suited for micromounting.  However, well formed crystals have been observed up to 2.5 centimeters from this locality.  To the upper right is an example of large pyrite crystals for the locality.  Large crystals are usually heavily distorted and irregular, occasionally showing multiple growth with more than one main crystal form.  Quality Pyrite specimens from this locality are highly valued by collectors of midwestern and Ohio minerals.  In addition, many well respected world-wide mineral museums house pieces from this locality.  These unique pyrite specimens are often naturally painted with a thin film of 

Iridescent Pyrite with Dolomite
(specimen Joseph W. Vasichko)
largest crystal measures .4 cm 
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio
iridescent oxidation or tarnish which greatly enhances the aesthetics of this simple sulfide.  This iridescence has been observed in virtually every color of the rainbow.  However, a quick wash with a toothbrush will return the crystals to a plain brassy yellow or silver color.   The most aesthetic Pyrite specimens typically have some iridescence and are  in association with Dolomite.

Large irregular multiple growth Pyrite crystals 
(specimen Douglas L. Core)
largest crystal measures 1.9 cm 
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


Pyrite with Dolomite
(specimen Joseph W. Vasichko)
largest crystal measures .3 cm 
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


 

Pyrite and Dolomite on Dolostone
(specimen Joseph W. Vasichko)
specimen measures 8.6 cm x 7.4 cm 
C.E. Duff and Son Inc. Quarry, 
Huntsville, Logan Co. Ohio
Pyrite Crystal Growth and Habits
    Few localities have yielded the number of diverse Pyrite crystal forms known to occur at Duff's.  Some of the crystal forms which can be readily observed at Duff's Quarry, generally in combination, include trapezohedral, diploidal, octahedral, cubic, pyritohedral and dodecahedral.  With this number of crystal forms, the possible combination of forms is extensive.  Many of the crystal forms observed at the locality are widespread throughout the quarry, while others have been very localized.   However, crystals from the same pocket and often the same zone typically exhibit identical crystal form.  The form may be distorted from crystal to crystal, but is usually easily identifiable.  With few exceptions, multiple crystal forms are not seen in one pocket.   Second generation octahedral Pyrite crystals have been observed, but these are quite rare and by no means the norm.   Typically, most larger crystals occur in the lower part of the upper level, in a layer where pocket size is unfortunately smaller.  Crystals found in the most heavily mineralized zones are generally no larger than 1 centimeter.  Several, more in depth, studies have been conducted on the pyrite crystal forms from this locality.  The following sections will explain and exhibit the more common of these forms.  The R. Peter Richards article, listed in the references, provides a more detailed analysis of many of these crystal forms.

 
The Forms of the Pyritohedral symmetry class of the Isometric System
    As previously mentioned, the C.E. Duff and Son Inc. Quarry is one of the few localities where a multitude of pyrite crystal forms can be observed.  To identify the forms which have been observed at this locality, it is first necessary to know and understand the seven basic geometric  crystal forms of the pyritohedral symmetry class of the Isometric system.  Fig A. To the right is a diagram of these geometric shapes.   Only the Diploid(F) and and the Octahedron(C) have been observed in unmodified form.   In general, unmodified crystals from this locality are quite rare.   While the most simple of these crystal forms is the Cube(A), it is the least commonly observed at this locality.   The most commonly observed unmodified crystal form is the Octahedron(C), which can be found as second generation crystals.  The Octahedron(C), perhaps the second simplest Isometric form, is formed by "cutting" a single triangular face on each corner of the cube(A).  Further, the Trisoctahedron(D) is formed by "adding" 3 triangular faces to each side of the Octahedron(C).  Similarly, the Trapezohedron(G) is formed by "cutting" 3 triangular faces to each corner of the cube.   The dodecahedron(B) is formed by cutting 12 quadrilateral sided faces between every two faces of the cube(A).  The pyritohedron can be explained multiple ways.   One way to produce the pyritohedron(E) is to construct 2 pentagonal faces on each of the 6 sides of the cube(A).  Another way to produce this shape, similar to the dodecahedron(B), is by cutting 12 pentagonal faces between every two faces of the cube(A).   The most common crystal form seen at the Duff Quarry is the Diploid(F), usually with Trapezohedral(G) modification.  The Diploid(F) shape is formed by doubling the sides of the Pyritohedron(E).  These geometric shapes dictate the crystal modifications which can be found at the C.E. Duff and Son Inc. Quarry.  To the lower right is a table of Pyrite crystal forms found at the Duff quarry with face names and miller indices.   It is highly unlikely that a pyrite crystal from this locality would have all of these faces, as certain faces are only found in combination with particluar dominant forms.   For instance, the pyritohedron(f 310) is not found on Trapezohedral(M 311) crystals, but is common on Trapezohedral(N 211).   Many other exclusive crystal relationships of this type also occur at this locality. 

fig A. The seven basic crystal forms of the Pyritohedral symmetry class of the 
Isometric system: A) Cube, B) Dodecahedron, C) Octahedron, 
D) Trisoctahedron, E) Pyritohedron, F) Diploid, G) Trapezohedron.  All of the 
forms B-G can be directly related to the cube.   All of these forms have been 
observed as modifications to the Diploid, Trapezohedron and Octahedron.
 
Cube(a)
Dodecahedron(b)
Octahedron(o)
Pyritohedron(e)
Pyritohedron(f)
Pyritohedron(e-)
Trapezohedron(n)
Trapezohedron(m)
100
110
111
210
310
120
211
311
Trapezohedron(q)
Trisoctahedron(p)
Trisoctahedron(r)
Diploid(s)
Diploid(u)
Diploid(d')
Diploid(d'')
Diploid(d''')
322
221
332
321
421
22.10.7
22.11.7
57.32.10
Chart A.  Miller indices of Pyrite crystal forms observed at the C.E. Duff and 
Son Inc. Quarry

 
Common diploidal crystal form
    Of the several Pyrite crystal forms known to exist at the C.E. Duff and Son Inc. quarry, the most common form is a diploid with trapezohedral modifications.    More than 90 percent of all Duff Pyrite crystals exhibit this crystal form.  This form is generally widespread throughout the quarry.  At first glance, these crystals look to be purely trapezohedral, a form not commonly observed in Pyrite.   However, closer inspection reveals that this form is dominated by the diploid with slight trapezohedral modifications.  Very few mineral species employ this crystal shape.  Figure B. to the right displays both the diploid(D) and the trapezohedron(T).   Without a goniometer the diploid and trapezohedron can be somewhat difficult to differentiate.  The angle which most clearly separates the two forms is labeled angle (a). In the diploid, this angle is clearly much sharper than its counterpart in the trapezohedron.   Figure C. to the lower left illustrates the diploid modified by the trapezohedron.  In Pyrite crystals from this locality, the trapezohedral modifications, labeled T in this figure, range from being extremely slight to clearly identifiable, but are usually

Fig C. diploid modified by the trapezohedron
smaller than the Diploidal faces, labeled D.  This modification doubles the basic 24 sided diploid into a 48 sided shape.  This new shape clearly exhibits both forms.   With the addition of the Trapezohedral faces,  the use of a Goniometer is no longer needed to identify and explain the crystal form.  The photo to the right is an example of a typical modified diploid.  Notice the clear trapezohedral modifications on this crystal, typical of most Duff Pyrite specimens.  Over 80 percent of the diploidal crystals from this locality will exhibit this modification.

Fig B. diploid(D) and trapezohedron(T) crystal forms


Pyrite showing clear diploidal shape with trapezohedral modification
(specimen Joseph W. Vasichko)
largest crystal measures .9 cm 
C.E. Duff and Son Inc. Quarry, 
Huntsville, Logan Co. Ohio


 
Modifications to the Diploid 
  While the Diploidal form with trapezohedral modifications is the most common crystal form observed at the Duff Quarry, it is not exclusive.   Figure D. to the right illustrates some of the modified diploidal crystal forms which are occasionally encountered at the Duff Quarry.  In a study of diploidal forms conducted for this article, the forms A-H represent one observable progression of crystal modifications.  Other progressions of this type can and do exist.  Additional modifications are possible, however no diploidal crystals with expanded form beyond form H were discovered in this study.  Crystals with modifications of unequal size are common.  For example, a diploidal crystal with octahedral modifications should have 8 equal sized symmetrical octahedral faces.  However, one diploidal pyrite crystal with octahedral modifications may have 8 octahedral faces of varying size.  Further, all 8 octahedral faces may not be present on every crystal. 

Fig D. Modifications to the Diploid.  Forms A-H show a possible progression of modifications. 
Other progressions can and do exist.  The progression of modifications above is as follows: 
A diploid(d'), B trapezohedron(m), C cube(a), D pyritohedron(e), E octahedron(o), 
F dodecahedron(b), G trisoctahedron(p), H trapezohedron(n).  Face names and miller indices 
may be found in fig. A above.

 

Fig E. trapezohedron(t) with 
pyrtohedral(e) modifications. Note 
trapezohedral faces do not always meet 
at a central point.
 


Fig F trapezohedral(t) with octahedral(o) 
and pyrtohedral(e) modifications

Common Modified Trapezohedral crystal form
    Although the diploidal habit is by far the most common crystal form observed at this locality, it is by no means the most complex.   Trapezohedral crystals are occasionally encountered throughout the quarry.  These trapezohedral crystals usually have pyritohedral and octahedral modifications.  True unmodified trapezohedrons are generally not encountered at this locality.  The pyritohedral modification creates a kite shaped quadrilateral face between two trapezohedral faces.  This pyritohedral face, labeled e, is visible in Figure E. to the upper left.  This face is commonly quite small in comparison to the trapezohedral faces, but occasionally has been observed to be of equal size to the trapezohedron.  The photo to the left exhibits a clear example of this pyritohedral modification to the trapezohedron.  In general, the pyritohedral face on this crystal is much larger than most from the locality.  Notice also that the four trapezohedral faces do not meet at a single point.   This is more common in the trapezohedral form than in the diploidal form.   The octahedral(o) modification is usually found in combination with the pyritohedral modification.  On a perfect crystal, this modification makes an equilateral triangular face between three unrelated trapezohedral faces.  Very rarely, will the octahedral modification be found on a trapezohedral crystal without the pyritohedral modification.  Figure F. to the lower left exhibits this form.  Occasionally, this modification is enhanced with a second trapezohedral modification.  In the photo to the left, the octahedral modification in the upper right corner has this additional modification.

Pyrite showing distorted Trapezohedral  shape with large 
pyritohedral modification
(specimen Joseph W. Vasichko)
crystal measures .2 cm 
C.E. Duff and Son Inc. Quarry, Huntsville, Logan Co. Ohio
 


Pyrite showing trapezohedral shape with large pyritohedral 
and octahedral modifications
(specimen John D. Vasichko)
crystal measures .4 cm 
C.E. Duff and Son Inc. Quarry, Huntsville, Logan Co. Ohio


 

Fig G. Modifications to the Trapezohedron  Forms I-O show a possible progression of 
modifications. Other progressions can and do exist.  The progression of modifications above 
is as follows: I trapezohedron(m), J pyritohedron(e), K octahedron(o), L diploid(d'), 
M trisoctahedron(p), N trapezohedron(n),  O cube(a).  Face names and miller indices may be 
found in Chart. A above.
Modifications to the Trapezohedron
  Similar to the progression of diploidal crystal forms, Figure G. to the left, forms I-O to avoid confusion with the diploidal crystal forms, shows a possible progression.  However, only forms J, K, M, and O were actually observed.   It is logical that forms L and N exist along with other combinations.  True, unmodified trapezohedral pyrite crystals I, have not been observed or reported and likely do not exist.  No predominately trapezohedral crystals were observed with additional modifications beyond form O, however it is conceivable that such crystals may exist.  Forms J and K, as mentioned above, are without doubt the most common of trapezohedral forms to be found at this locality.  Like the diploidal crystals, these crystal forms are often somewhat irregular, especially in larger crystals.  Although the faces of these crystals are generally sharp, similar faces of varying size are common.

 
Other Complex Pyrite Crystal Forms
  Several other Pyrite crystal forms are regularly encountered at the C.E Duff and Son Inc. quarry.  Among these other forms, the most commonly observed are illustrated in Figure H. to the right.  Combined, these forms account for less than 2 percent of all the Pyrite crystals found at the locality.   Forms A, B and E are dominated by the pyritohedron.  True pyritohedral crystals are generally not found at this quarry.    Below is an example of form A.  Notice the large pyritohedral face.  This form could have been included with the trapezohedral crystal shapes in fig. G above and would be similar to Form M with an enlarged pyritohedral face.  Forms B and E are quite similar, with  the employment of the trapezohedron(211) instead of the trapezohedron(311) and a noticeably larger cubic face.  Form C, pictured to the far lower right, is dominated by the octahedron and is perhaps the most common of these other forms.  This is the only complex form regularly seen with large octahedral faces.   Form D is dominated by the diploid, but is 

Pyrite crystal showing Form A dominated by the 
pyritohedron and trapezohedron with diploidal,
trisoctahedral  and octahedral modifications. 
C.E. Duff and Son Inc. Quarry
(specimen Joseph W. Vasichko)
crystal measures .3 cm
noticeably different from other diploidal forms seen at the Duff quarry.   This form employs faces from 3 different diploidal shapes (d',d'',d''') and a rarely seen trapezohedral(q) face.  An example of this shape is pictured to the immediate right.  Many other forms can and do exist at this locality.  However, these are the most frequently seen. 

Fig H. Other complex Pyrite crystal forms occasionally encountered at the Duff Quarry.
Many additional forms have been identified but these are the most frequently observed. 
Forms A, C and D are the most common of these forms and are pictured below.  Forms B and
E were not photographed for this article.   Crystals dominated by the trisoctahedron, cube
and dodecahedron were not observed.
 
Pyrite crystal showing Form D.
Crystals have been slightly etched,
but the form is still clear. 
C.E. Duff and Son Inc. Quarry
(specimen Joseph W. Vasichko)
crystal measures .4 cm.
Pyrite crystals showing Form C.  Notice the large 
octahedral faces.   This crystal form is often 
somewhat distorted.
C.E. Duff and Son Inc. Quarry
(specimen Joseph W. Vasichko)
Crystal on the Right measures .4 cm.

 
Second Generation Octahedral Pyrite
  Infrequent second generation Pyrite crystals have been observed at the Duff Quarry.  In general, these crystals are dominated by the octahedron.  Occasionally, these can be true unmodified octahedrons.  However, the more common form is an octahedron with trisoctahedral and cubic modifications as described in figure I below.  These second generation crystals are more commonly observed in Pyrite pockets with Dolomite.  Although pyrite crystals at this locality will grow quite large, the average second generation 

Fig I octahedron with 
trisoctahedral and cubic 
modifications 
crystal is less than 1 mm in size.  Second generation crystals which grow on earlier Pyrite are typically not well attached, and often decay rapidly into melanerite.  In contrast, these same crystals when attached to Dolomite seem to be more stable and have an iridescence similar to other pyrite from the locality.  The Pyrite crystal in the photograph to the right is an example of second generation Pyrite.  Although this crystal formed on Dolomite, there were similar crystals in the pocket on Pyrite which were unstable and did not survive to be photographed.
 

Second generation Pyrite, octahedron with trisoctahedral and cubic 
modifications on Dolomite.
C.E. Duff and Son Inc. Quarry
(specimen Joseph W. Vasichko)
crystal measures .08 cm

 
Fluorite  CaF
       Although the C.E. Duff and Son Inc. quarry is best known for fascinating pyrite specimens, perhaps the most sought after mineral from this locality is  Fluorite.   Good Fluorite crystal specimens are extremely difficult to collect from this quarry.   The most common occurrence of Fluorite, which is regularly encountered at the base of the upper level, is golden to brown massive. This massive Fluorite is similar to Fluorite from other Ohio localities and fluoresces bright cream under short, mid and long wave ultraviolet light.  Small crude brown Fluorite crystals with Calcite have also been reported with massive.  Clear, yellow, gold, brown and purple crystals are extremely uncommon, but have been observed with Dolomite, Calcite, Pyrite and Sphalerite.  Occasional crystals are zoned purple, clear and yellow.   Fluorite crystals which are completely exposed in the pocket or are only partially embedded in Calcite are always heavily water etched and crude.  The sharpest crystals are usually found completely embedded in Calcite.   Unfortunately, many Fluorite crystals found completely under Calcite, are also etched.  Only the rarest of crystals is sharp.   The best crystals are found by carefully dissolving the Calcite with muriatic acid, so as not to harm the Pyrite, Fluorite, or Dolomite(when possible).  The photo to the upper left exhibits a purple cube with Dolomite and Pyrite in a dolostone pocket.  This specimen has been slowly etched out of Calcite with extremely dilute   

Fluorite on Dolomite
(specimen John D. Vasichko)
specimen measures 6.8 cm x 4.6 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio
muriatic acid.  This process accounts for the sharp nature of this crystal.  This Fluorite crystal has phantom purple edges similar to crystals from the Bluffton Stone Co. Quarry, in Allen County, but is more raspberry in color.  A careful eye will notice the clarity of this purple crystal.  Most, Fluorite crystals from the Duff Quarry also have frosted centers.  The photo to the left displays a typical golden yellow crystal on Dolomite.  This specimen was also slowly etched from Calcite to preserve the Dolomite crystals.   The crystal in the photograph to the lower right was not removed from Calcite and is more typical of Fluorite crystals from this locality.  Notice the heavily water etched faces.  This clear crystal with purple phantomed centers and yellow zoning is more reminiscent of Fluorite crystals from the Stoneco Inc. Auglaize Quarry, in Paulding County. 

Fluorite with Pyrite and Dolomite
(specimen Joseph W. Vasichko)
specimen measures 5.4 cm x 3.6 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


Fluorite with Pyrite and Dolomite
(specimen John D. Vasichko)
crystal measures 2.2 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


 
Calcite  CaCO3
    One of the most common minerals found in quarries throughout Western Ohio is Calcite.  However, it is only rarely seen in good crystals at the C.E. Duff and Son Inc. Quarry.  Typically, Calcite is found as white to gray cleavable massive as pocket and crevice fillings.  This massive Calcite came after other mineralization.  Many of the best Pyrite specimens  from the Duff quarry are prepared by dissolving this Calcite with dilute mutiatic acid.  Occasionally crystal faces can be seen in pockets where this massive Calcite did not completely fill the vug.  Unfortunately, these rarely make good mineral specimens.  Massive white Calcite from this locality can be slightly fluorescent bright blue under short wave ultraviolet light, but this is not the norm.  The best crystal specimens of Calcite are typically small, golden tan in color and are often in combination with Dolomite.  The most common Calcite crystal form observed at this locality is rhombohedral.  However, tiny, unaesthetic scalenohedral crystals have also been reported.  Golden tan Calcite crystals from this locality may or may not be fluorescent cream under short, mid and long wave ultraviolet light.  Although occasional small Calcite crystals were encountered with Pyrite and Dolomite, most of the better and larger Calcite crystals were found in the Northern part of the upper level.   The photo to the upper right is an example of typical Calcite found in the Southern part of the quarry.  On average, crystals from this part of the quarry measure less than 3 millimeters and are somewhat gemmy.  Even the  

Calcite with Dolomite
(specimen John D. Vasichko)
crystals measures app. .7 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio
smallest Calcite crystals often have a melted or rounded appearance.   The photo to the lower right is a fine example of larger Calcite crystals from the C.E. Duff and Son Inc. Quarry.  Notice the crystal form is more distorted on these water etched crystals.  It is also important to note that as these crystals grow larger, they become milky and distorted.  Crystals over 2 centimeters are typically crude and often lose the rich golden color afforded smaller crystals.   The crystals in the Calcite group to the left are partially clouded.  Larger crystals are often completely clouded in this manner.

Calcite on Dolomite
(specimen Joseph W. Vasichko)
crystal measures .5 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


Calcite on Dolomite
(specimen Douglas L. Core)
Calcite crystals are rougly 1 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio


 

Dolomite
(specimen Joseph W. Vasichko)
crystal measures .5 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio
Dolomite  CaMg(CO3)2
        While the C.E. Duff and Son Inc. quarry is perhaps the premier Ohio locality for curved rhombohedral, commonly called saddle shaped, Dolomite, it is without doubt the least appreciated mineral to be recovered.   In part, this is due to the relative abundance of quality pink to orange Dolomite crystals from other Midwestern localities.  While Dolomite crystals from this locality can certainly compete in form, the dull buff white to cream color is not as aesthetic or appealing as the color from other midwestern localities including Corydon, Indiana and Rush, Arkansas.  Also, Dolomite crystals are fairly easy to collect throughout the quarry.   Dolomite occurs as cream to white rhombohedral crystals lining pockets and crevices.  Most horizontal crevices in the dolomitic limestone are coated with tiny rhombohedral crystals.  Although the form is curved, the smallest crystals often appear as true rhombohedrons,   As these crystals become larger, the curved form becomes increasingly noticeable.  Similar specimens can be found in most of the quarries throughout the Tymochtee Dolomite, but this locality is recognized as the most prolific for the species.   The photo to the left displays a typical example of buff white Dolomite crystals from this locality.  Most collectors prefer Dolomite specimens in combination with other minerals, especially Pyrite.

 
Sphalerite  ZnS
        Without doubt, the most difficult mineral to be recovered at the C.E. Duff and Son Inc. quarry is Sphalerite.  Sphalerite is generally found as small, sharp, dark red, hextetrahedral crystals lining pockets and crevices with Dolomite.  The best Sphalerite crystals were commonly observed at the base of the upper level.  Recently, Sphalerite has been more common in the second level of the quarry.  Unfortunately, pockets larger than 1 cm are rare in this part of the operation. 

multiple growth Sphalerite with Dolomite
(specimen Joseph W. Vasichko)
crystal measures .3 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio
Sphalerite will form sharp, dark, ruby jack, single crystals up to 3 millimeters, or infrequent twinned multiple growth crystal clusters up to 1 cm.  Multiple growth crystal clusters of that size are extremely rare.  The photo to the left displays typical multiple growth crystals from this locality.   In contrast, the photo to the right displays the more common Sphalerite crystal habit from the Duff Quarry.  Due to the uncommon nature of this species at the Duff Quarry, quality specimens of Sphalerite from this locality are typically well appreciated among knowledgeable collectors. 

Sphalerite
(specimen Joseph W. Vasichko)
crystal pocket measures 2.3 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio

 
Summary
        At this point, this collector would like to thank the owners of the C.E. Duff and Son Inc. Quarry for their past generosity of allowing specimens to be preserved for study.  Many at this operation are aware of the tremendous significance of these specimens to mineralogists, mineral enthusiasts and educators both locally and world-wide.    The study of the mineral habits at this locality are especially important to a more complete understanding of Ohio mineralogy.  Without their generosity, this type of study would never have been possible.   Their understanding and regard for such research is greatly appreciated.   The many years of limited and controlled safe collecting made available through their kindness has afforded collectors with high quality specimens from this classic Ohio locality.  It is the hope of this collector that this information will help mineral enthusiasts understand and more greatly appreciate the history and development of minerals from this locality.   Unfortunately, this article cannot attempt to cover every mineral habit which occurs or has occurred at the C.E. Duff and Son Inc. quarry.  Mineralogically speaking, this fruitful quarry has surely produced other distinct mineral forms in its nearly 50 years of operation.  Certainly, further study is warranted on the many complex pyrite forms and other mineral habits found at this quarry.   For other related information on the minerals of this locality, see the reference list below. 

Calcite on Pyrite and Dolomite
(specimen Joseph W. Vasichko)
specimen measures 3.4 cm x 2.8 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio

   This article in no way grants the reader permission to collect in the C.E. Duff and Son Inc. quarry.  Permission must be obtained before entering any active mining area or collecting on any posted private property.
 
 
References
Carlson E.H., 1991, Minerals of Ohio: Ohio Division of Geological Survey 
Carlson E.H, 1990 "Ohio Mineral Locality Index" Rocks and Minerals vol 65 
           no.6, Heldref Publications 
Dana, E.S. and Ford, W.E., 1932, A textbook of Mineralogy( 4th ed.):New 
          York, John Wiley and Sons 
Gait R.I., 1978 "The crystal forms of Pyrite" Mineralogical Record 
          vol 9 219-229
Gait R.I., 1980 "Pyrite Crystals from Duff's Quarry, Huntsville, Ohio USA" 
          Mineralogical Record vol 11 97-99
Janssens, Adriaan, 1977, Silurian rocks in the subsurface of northwestern 
          Ohio: Ohio Division of Geological Survey Report of Investigations 100 
Korbel, P. and Novak, M., 1999, Minerals Encyclopedia, Rebo International 
Richards, R. Peter, 1987 "Pyrite Crystals from the Duff Quarry" 
          Mineralogical Record vol 18 no.6 391-398
Sinkankas, John, 1964, Mineralogy for Amateurs, Van Nostrand Company
          Inc.
Stout, W.E. 1941, Dolomites and Limestones of western Ohio: Ohio Division 
          of Geological Survey Bulletin 42 
Wolfe, M.E., 1997, Report on Ohio Mineral Industries, Ohio Division of 
          Geological Survey 

Pyrite and Dolomite
(specimen Joseph W. Vasichko)
field of view measures 6.9 cm x 4.8 cm
C.E. Duff and Son Inc. Quarry
Huntsville, Logan Co. Ohio