Microminerals of the Buckwheat Dolomite
ALBITE forms transparent, colorless crystals, usually twinned. See Figs. 11 and 13 (Band 3, Tafel 169), Fig. 52 (Band 3, Tafel 171), and especially Fig. 64 (Band 3, Tafel 172) in Victor Goldschmidt's Atlas der Krystallformen. Additional figures that resemble Buckwheat albites are 156, 180, 199, 245, and 269.
ANATASE: The rarest polymorphic form of titanium dioxide, anatase forms bluish, bipyramidal crystals. Only a couple of people have ever found anatase specimens in the Buckwheat dolomite. It occurs rarely at this locality.
AURICHALCITE: A basic carbonate of zinc and copper, aurichalcite is relatively rare at Franklin but can be found if you are persistent. It appears as green, bluish-green, or light blue tufts of needle-like crystals; it can also be found as very thin plates. Aurichalcite is most likely to occur in the more-weathered ("rotten") dolomite on the dump.
AZURITE: A basic carbonate of copper, azurite can be confused with aurichalcite but is almost always deep blue. It forms bladed, tiny crystals. I have seen only one specimen of "azurite" in the Buckwheat dolomite so far, and I'm not even sure that was really azurite. It might have been blue paint from someone's Estwing chisel. Apparently, azurite is rare in the dolomite; actual crystals of it would probably be scarcer than anatase.
BROOKITE is titanium dioxide, a polymorphic form of rutile.
This mineral can be brown, reddish-brown, bluish, or black. Broken surfaces
have an adamantine luster somewhat like that of sphalerite. Brookite crystals
are flattened, tabular, or sometimes prismatic, and they normally have striated
faces. When brookite is found, rutile often accompanies it. Its crystal
form distinguishes it from sphalerite... that is, if you happen to find
good crystals. NOTE: many claimed "anatase" specimens from the Buckwheat
are actually blue brookite. Crystal form is the indicator here. Beginners
also tend to confuse brookite with sphalerite. While the former's
crystal habit is different, there is also a very subtle difference in the
color and surface appearance; brookite has a more "smoky" appearance.
It is hard to describe but can be learned through visual comparison
of many known specimens.
CALCITE (CaCO3): Often you can't tell this mineral from dolomite, at least when it forms the usual rhombohedrons. The two minerals look almost exactly the same, are both carbonates, and occur together. However, calcite sometimes forms clear, pseudo-octahedral crystals that look like tiny diamond crystals. They can be very tiny, often requiring 30 or 40x magnification. They are uncommon, but I stumbled upon one cavity in a piece of dolomite that contained 4 or 5 calcite pseudo-octahedrons. These interesting crystals can be found with rutile and of course dolomite. Some larger (1-5 mm) calcite crystals occur on the Buckwheat dump, showing a form I'm not sure what to call; they vaguely resemble tiny, flattened soccerballs. There are also crystals of approx. 1-2 mm diameter that strongly resemble Figures 131 and 144 (Band 2, Tafel 9) in Victor Goldschmidt's Atlas der Krystallformen; these tend to occur near the colorless albite twins mentioned above.
CHLORITE (CLINOCHLORE) is a micaceous mineral which occurs
as tiny aggregates of green or gray-green plates. They appear hexagonal
(like mica) but are said to be pseudo-hexagonal in actual form. Clinochlore
can be confused with lennilenapeite or muscovite.
FLUORITE is uncommon in the Buckwheat dolomite, but actual
crystals of it seem to be exceptionally rare. Of the fluorite samples we've
collected from the dolomite, all are violet to colorless masses or cleavage
fragments; no crystals have yet surfaced for us.
HEMIMORPHITE: I once found a tiny "pinwheel" of what is most likely hemimorphite. This mineral is not all that rare in the Buckwheat dolomite, but well-formed crystals are usually very small.
HYDROZINCITE: formed as an alteration product of sphalerite, this mineral is often found as dull white coatings on the outsides of dolomite boulders on the Buckwheat dump. Closer inspection can reveal nice specimens with well-formed micro-spherules which may fluoresce a bright blue-white under SW UV. May be confused with smithsonite, which also occurs as coatings on the dolomite (but does not fluoresce as brightly or in the same color)
LENNILENAPEITE is a greenish-gold micaceous mineral which
occurs in the Buckwheat dolomite and is quite rare anywhere else in the
world. It could be mistaken for clinochlore, which also occurs here. Lennilenapeite
is a phyllosilicate and is part of the stilpnomelane group, which also includes
franklinphilite (and of course stilpnomelane). The lennilenapeite
that occurs in the Buckwheat dolomite is normally dark, olive green; that
occuring in the feldspar is sometimes a golden color, although it seems
possible this could be a related mineral species and not lennilenapeite.
MICROCLINE has an unusual appearance in the Buckwheat dolomite;
it occurs not as white or green blocky masses, but as pale lavender
bunches of crystals that are sometimes elongated or sheaf-like and often
have concave surfaces. I had always assumed this material was albite
(see above), but I'm told it's really microcline. It can be found
fairly easily in the dolomite and is sometimes discernible without magnification.
MONAZITE (Ce) occurs as translucent yellow crystals, often all by themselves on the dolomite. Sometimes these yellow crystals have a faint pinkish hue. Monazite can be confused with the uncommon, yellow variety of sphalerite or with the rare synchysite-(Ce). However, if you find a well-formed crystal, you should be able to tell what it is. Monazite was first verified from the Buckwheat dolomite during the 1980's. Experienced collectors know the dolormite well enough to pick out pieces that are most likely to contain monazite. Just remember that these monazites are very tiny; though a 10x loupe can help you locate them, 30 to 40x magnification is often necessary to see their features.
PYRITE is found commonly as well-formed "pyritohedrons" (with
pentagonal faces). These often have a reddish coating of hematite on some
of the faces, giving a pleasing appearance. They are most often found in
the dark-gray rock that occurs as intrusive bodies in the dolomite. If you
are really persistent, you might find the rare dodecahedral form of pyrite
from the Buckwheat dolomite.
RUTILE is the common polymorphic form of TiO2.
Rutile is not that hard to find in the Buckwheat dolomite, either, but the
crystals are invariably tiny (!) and needle-like. Sometimes they
are intergrown like a straw mat, but a few specimens occur as needles that
radiate neatly from a central point. The crystals are usually terminated,
but the terminations are so small that you may as well forget seeing them
with an optical microscope.
SMITHSONITE, a zinc carbonate, occurs as coatings on dolomite and on quartz crystals; less often it occurs as rosettes and sheave-like aggregates. Single crystals also occur; the crystal form is hexagonal. Expect the crystals to be very, very small if you do happen to find them. Smithsonite can occur with rutile and sphalerite, and hydrozincite can often be nearby.
SPHALERITE is zinc sulfide, often with some iron (i.e, (Zn,Fe)S). It forms brown, yellow, black, oil-green, or reddish-brown tetrahedral crystals, often sharply formed. Broken surfaces have an adamantine luster. In many cases there are triangle patterns on the triangular faces of each sphalerite tetrahedron. Sphalerite is frequently found as spinel-law twinned crystals, often near pyrite and rutile; these sphalerites can often be seen without a loupe. This mineral can be confused with brookite, but the crystal structure is different. Sometimes sphalerite crystals in the Buckwheat dolomite look like octahedrons... unless these "octahedral" crystals are actually some other mineral (such as zircon).
STILPNOMELANE: There is definitely a stilpnomelane-group mineral
(or two) to be found in the Buckwheat dolomite. Chances are that you will
find lennilenapeite (see above), though you might have to search carefully.
It is possible that you could find franklinphilite. Look for micaceous or
foliated masses. Lennilenapeite contains zinc and manganese; stilpnomelane
does not. In the Franklin formation it's likely that the minerals you find
will be zinc-bearing in some proportion or another, so "true" stilpnomelane
(i.e., pure, end-member composition) seems unlikely.
SYNCHYSITE-(Ce): I found one, only 0.25 millimeters
across, sitting next to a pyritohedral pyrite crystal of similar size. The
crystal form is different from that of monazite. The putative synchysite
crystal is yellow and fluoresces very faintly green in unfiltered shortwave
UV. A couple of other collectors have also found synchysite at Buckwheat.
TALC (Steatite): Light gray-green to almost white micro-spherules
and massive coatings occur in and on many of the dolomite specimens I've
found on the Buckwheat. This talc typically has a soapy luster that
is unlike any of the other minerals with which it's likely to be found.
Some pieces of the ore-dolomite contact rock are 30 cm wide or more, but check them with your UV lamp and you'll see the willemite doesn't go all the way through the rock. Somewhere out there I'm sure there's a perfectly-formed, isolated willemite crystal sitting in a pocket of the classic "sugary" dolomite, but I'd imagine it doesn't have much company.