Get off the beaten path... If you want to find those mom-and-pop joints, those funky little places, just ask around. Guy Fieri
I often bemoan the fact that certain items are
disappearing from the American roadside, things like drug stores with ice cream
and shakes, general stores, non-chain hamburger stands, and especially “mom and
pop” rock/mineral/fossil stores. I
suppose that my age and nostalgic thinking make these disappearances seem
severe when in reality you can order any mineral that pops into your mind from
a web business (now ice cream is a little tougher). But there is, to me, something special about
pulling open a dusty drawer in an old cabinet and taking a lighted loupe to
examine a dusty specimen with old hand-written labels. I am always on the lookout for these stores
and make an attempt to locate and patronize these establishments. On the other hand, it is tough to make a
living selling minerals for a buck or five and most of these stores seem a
labor of love.
I recently took a little road trip and stopped at one
of my favorite old timey stores and begin sneezing while blowing dust off some
of the drawer specimens—not many other tourist patrons bother with the drawers. Not really needing any new minerals, I still
made a purchase of some interesting specimens at “cheap” prices. So, what little jewels did I come home with
(only a partial list)?
The very
reason I collect and write about minerals is so
I might not sleepwalk through my entire life. Apologies to Zadie Smith
Bisbee, Arizona, is known to rockhounds and
mineralogists through the world. The
Copper Queen Mine and the Lavender Pit Mine have produced an array of secondary
copper minerals that are considered classics.
Rock and mineral shows have devoted their attention and themes to Bisbee
minerals. And virtually any mineral collection,
at least here in the states has a beautiful specimen of blue Bisbee azurite and
usually one of green malachite. However,
I needed something new from Bisbee and spotted a thumbnail with antlerite, a
copper sulfate hydroxide [Cu3(SO4)(OH)4]. Antlerite is found as a secondary mineral in
the carbonate-poor, oxidized zone at many copper mines but is never
common. In fact, Anthony and others
(1995) noted it was rare and in mines of the Bisbee area was collected from the
Copper Queen Mine (probably) as small crystals of excellent quality implanted
on brochantite. Antlerite ranges from
emerald-green to light green to blackish green in color. Crystals are vitreous, translucent, brittle
and soft (~3.5 Mohs) and leave a pale green streak. Most crystals are thick tabular, or equant or
short prismatic. They also occur as
rather non-descript granules or aggregates of fibrous crystals.
By the time mineralogy class rolled around students
were introduced to a variety of garnets and learned that “garnet” was not a
legitimate mineral name but referred to a group of silicate minerals differing
in composition but crystallizing in the same system (Isometric), and their
mineral properties such as hardness, cleavage and density were all very
similar. Usually the specimens studied were almandine [Fe2+3Al2(SiO4)3],
pyrope [Mg3Al2(SiO4)3], spessartine
[Mn2+3Al2(SiO4)3],
andradite [Ca3Fe3+2(SiO4)3],
and grossular [Ca3Al2(SiO4)3]—all
end members in the Garnet Group. Things
got more difficult in graduate-level courses in igneous and metamorphic
mineralogy/petrology and instructors added uvarovite, also an end member, [Ca3Cr2(SiO4)3]
to the list for study. Chemical formulae for members of the Garnet Group is X3Y2Si3O12
where X includes the divalent (2+) oxidation charge cations like Ca, Mg, Fe,
and Mn while Y represents trivalent cations (3+) oxidation charge like Al, Fe,
and Cr; all cations are clustered around the silica tetrahedra. Today MinDat
lists 14 different minerals belonging to the Garnet Group with many of these
types having numerous varieties. For example, spessartine has at least six
varieties while grossular parades out 15 varieties including the popular, and
expensive, green tsavorite with coloring supplied by chromium and vanadium. Garnet
Group members have two solid solution series: 1) pyrope-almandine-spessartine;
and 2) uvarovite-grossular-andradite. Essentially all colors of the rainbow are
present in some variety of garnet since rare blue colored specimens were
discovered a couple of decades ago.
At the rock/mineral shop I picked up a small cluster
of andradite crystals. This species has three major varieties: melanite
(black), topazolite (yellow-green), and the uber expensive demantoid (green). My find of mineral store garnet crystals is
the rather unusual andradite variety termed melanite or titanium garnet. These are black garnets where the titanium
evidently replaced or comingled with the silicon since the titanium (up to
~11%) appears as titanium oxide. The
crystals are dodecahedrons with an adamantine luster and a hardness of ~6.5-7.0
(Mohs), and a white streak. They are
pretty opaque but will partially transmit light from a rear source. Unlike
other garnets that usually form in metamorphic environments, melanites with
their titanium often form in alkaline igneous rocks (low silica), but also in
serpentine, skarns, crystalline schists, and iron ores. The locality
information, simply “New Idria Mining District, San Benito, CO, California.” This District is famous for world class
benitoite, neptunite, topazolite and melanite andradite garnets. I believe the
garnets formed in a skarn, a metamorphosed limestone intruded by hydrothermal
solutions heated by nearby intrusions.
The Spruce Pine Mining District in North Carolina is
one of the best-known mining areas in the U.S.
It is in a beautiful area of the Blue Ridge Mountains centered in
Mitchell and Yancy Counties and mineral-wise is famous for gem specimens of
beryl--varieties aquamarine, emerald, heliodor, and morganite. North Carolina is the country’s largest
producer of feldspar and original mines centered near Spruce Pine and produced
from a Precambrian pegmatite; however, current production is from “alaskite” (a
variety of granite) described as a very “coarse-grained, light-colored,
feldspar-quartz-muscovite rock. Composition of the rocks averages about 40
percent plagioclase (soda-spar), 25 percent quartz, 20 percent microcline
(potash-spar), and 15 percent muscovite” (information gleaned from North
Carolina Geological Survey at deq.nc.gov).
The Spruce Pine area is also the major producer of sheet mica, scrap
mice and olivine in the U.S., as well as a number of other industrial minerals.
The specimen I picked up is an intrusive igneous rock
with various feldspars, schorl (a black tourmaline), quartz, and a nice golden
beryl crystal that was collected from the Ray Mica Mine near Burnsville in
Yancy County. I have been through Burnsville a few times on my way to lodging
in Little Switzerland, and while traveling along the Blue Ridge Parkway, a
scenic 469-mile road running near the crest of the Blue Ridge and connecting
Great Smoky Mountain National Park in the South and Shenandoah National Park in
the north. The Blue Ridge is the high
part of the Appalachian Mountains with a variety of crystalline rocks emplaced
during continental collision and subduction generally termed the Grenville
Orogeny or the Grenville Cycle. At any
rate, the Grenville was not one major event but a series of orogenic phases
from ~1250 Ma to ~980 Ma, or somewhere around there, with the end result being
the formation of the Supercontinent Rodinia.
There were additional granite emplacements somewhere around 700 Ma due
to rifting of Rodinia. The Paleozoic
history of the Blue Ridge and the Appalachian Mountains is a “whole nother
story.”
I enjoy it; my experiences in traveling and looking at the rocks have taught me the importance of an open mind and have given me a willingness to wander off the beaten path - not only to keep life interesting, but also to understand in a meaningful way that things do not look the same from every vantage point.
Apologies to Esther Dyson
REFERENCES CITED
Anthony, J.W., S.A. Williams, R.A. Bideau, and R.W. Grant, 1995, Mineralogy of Arizona: The University of Arizona Press, Tucson.