York River Skarn Zone Near Bancroft, Ontario, Canada

As Published by Rock and Gem Magazine, November 1999

 

by Michael Walter

(Please note this site is now a Canadian Provincial Park and,

as such, collecting minerals at this site forbidden)

 

Purple zircons such as this one were a super rare find at the York River Scarn Zone near Bancroft, Ontario, Canada.       Here is a large cluster of grossulars, clinopyroxene and brucite.    This world class garnet (grossular) is only one example of the outstanding mineral specimens that are found at the York River Scarn Zone near Bancroft Ontario, Canada.  Other minerals include clinopyroxene, zircon, cancrinaite, biotite and brucite.



York River Skarn Zone Produces Fabulous Specimens

Thousands annually visit the mineral collecting capital of Canada, Bancroft,
Ontario.  Almost as many go to one of the most accessible public sites to
have their try at collecting the well formed grossular garnets on the edge
of the York River.  Known to most as the York River (Tactite) Skarn Zone,
this collecting location is a short drive on route number 28 east out of
Bancroft.  The site is a northerly trending belt of contact metamorphosed
calc- silicate rock.  Nestled on the side of a small, yet, steep hill the
site can also produce a host of other minerals as our visits in the summer
of 1997 proved.

This story more appropriately begins with my first visit to the York River
Scarn Zone back in the early 1970’s.  As a teen my Father, Jay Walter,
exposed me to the joy of mineral collecting.  Though, we had many famous
locations to visit at home in St. Lawrence County, New York, one of our
luxuries was to visit nearby Ontario, Canada.  One of my least impressive
memories was of the York River site.  The guide books all noted exotic
minerals not common in our state: grossular garnets, vesuvianite, zircons,
spinel, cancrinite, brucite and others.  I found none of these.  Not so much
as a flake of biotite.  Given my dismal impression of this collecting area
as a youth it is no small miracle that I ever took the opportunity to
revisit this site.  Quite by chance I did.

During the month of July my Father and me left for our annual trip to
collect minerals at the multitude of sites which surround the Bancroft
region.  This morning began with the 3 AM alarm going off.  After a quick
shower we staggered our way to the van, pre-packed, gased and ready for the
road.  I dare not think about what this trip would be like without a large
travel mug of strong coffee.

After a four hour drive we were in downtown Bancroft at 8 Am on a Monday
morning.  Two of the firsts tasks of our pilgrimage were always to go to a
local bank to exchange our American dollars for Canadian and to visit the
Chamber of Commerce to chat with the staff geologist, Chris Fouts.  Since
neither the bank nor the Chamber of Commerce were open we decided to kill an
hour or so by visiting the York River site.  With no intent to collect
minerals during this visit we walked around the small exposure on the
hillside noting the areas which appeared to have been recently worked.  No
garnet or, for that matter, any other minerals were seen in the scraps left
by previous collectors.  I did manage to lever out three or four chunks of
calcite from under a ledge which looked like they might hold specimens.  
These could be etched with acid at home to find out for sure.  In general
the site looked as if it had been totally cleaned out.

Happy to leave this deer fly infested location we returned to town for
banking and our visit to the Chamber of Commerce.  At the Chamber of
Commerce Chris Fouts informed us that he would be taking a tour group to the
York River site to collect on Thursday of that same week.  In my mind I was
saying, “Why?”, because it looked as if the site had been worked hard and
not producing.  Chris then told us about two seams of blue calcite that most
recreational collectors seldom notice.  As he described it, most people
pulled material from the ledge and in turn it ended up covering the true
collecting area at their feet.  These calcite seams ran almost straight down
and were to be found by removing the talus left by previous collectors.  
This new information gave insight as to why there seemed to be nothing at
the site to be collected.  We had been standing on three to four feet of
talus that was covering the place where we should have been digging.
Numerous other sites were on our agenda for the next few days,

so not giving the York River Scarn Zone another though, we wasted no time in
visiting them.

A week or so later I was at home etching some of the materials gathered form
the five days of collecting we had done in the Bancroft area when I came
upon the York River calcite collected that Monday morning.  Once etched I
was in for a shock.  What once appeared to be blocks of calcite and
non-mineralized wall rock were transformed into several large plates of
matrix coated by beautiful brown and orange garnets.  Mixed in among the
garnets were deep green clinopyroxenes and some small, but, well formed
brown vesuvianites.  Having seen other specimens from this site at mineral
shows and in museums I was aware that the specimens we had found were
outstanding.  The garnets were larger than most I had seen. While most
specimens from this location average one forth to three fourths of an inch
some of the ones we had found were one to two inches in diameter.  They were
well formed twelve sided garnets that always seemed to be in contact with
other garnets or matrix rock.  We found no true “floaters” in the material
we had brought home.  Even so these clusters were impressive.  Some of the
garnets were a reddish brown with gemmy sections while the second type was a
dull orange color showing no transparency what so ever.  It was not uncommon
to find both varieties in a single cluster.

After discovering what type of specimens could be obtained after the calcite
was etched away I was excited to say the least.  This prompted a series of
follow up trips which involved the removal of many large blocks of calcite
to be etched later.  It was important to try and obtain sections of calcite
that were in contact with the metamorphic host rock.  If blocks could be
removed that had host rock attached, the grossular garnet specimens would
often be found coating the matrix material.  In better specimens
vesuvianites would be found on or intergrown with the garnets.

The third trip to the York River Scarn Zone became the most exciting of the
summer.  My Father and me arrived at the site at 8 AM sharp only to find a
camper parked on the dirt road near the site.  Though no one was digging at
that early hour it was assumed by us that this was a fellow rockhound
planning to explore for garnets.  After about forty minutes of digging the
campers joined us at the location where we were digging into a calcite vein.
  The father explained that he and his son had been digging at the site the
day before and would be staying for at least another day.  They were also
looking for garnets.  Their purpose, however, was slightly different from
ours.  What they were doing at the site was sifting and washing the rubble
left behind by previous visitors to the site.  The small gemmy chips were
their prizes, later to be faceted into small gems.  I was surprised having
never heard of anyone collecting cutting material here before.  It was
amazing to see the beauty these garnets have when faceted.  Though the color
of the crystal specimens from the site ranges from a pale orange to a deep
reddish brown, the red crystals are the only ones which seem to have the
gemmy translucence required for faceting a quality stone.  Because the gemmy
sections in these specimens are small, in turn, so are the gems created from
them.  Just the same, the stones have a unique red color and a fiery
appearance in a setting.

After a lengthy discussion about what the faceting material looked like with
our new acquaintances it was back to digging for crystals.  The spot we
chose to dig was where two light blue calcite seams approximately two feet
wide each dip almost straight down into the country rock.  As with every
trip to this sit we had to remove one to three feet of overburden left on
top of the calcite veins.  They are not as obvious as one might think and so
most collectors accidentally cover them while digging directly into the
ledge itself.  Once the overburden was gone the process of finding fractures
and seams to chisel into began.  We cleared enough room for both of us to
dig but it was still cramped quarters.  Making it more difficult is the fact
that we had to dig directly below our feet.  It is quite difficult to
determine what areas of the calcite will hold crystal specimens.  In some
cases the edges of crystals might be visible while in most case the better
specimens are well hidden in the calcite itself.  If the crystal becomes
exposed it is usually partially or totally destroyed.  Because of this we
would usually remove pieces, as large as we could manage, and take them home
intact.

While I was in the process of removing 1 to 2 foot wide blocks of calcite
from the vein I noticed my Father taking a different approach.  Working only
a few feet away from me he was setting a series of large wedges into a
fracture  between the wall rock and a sizable slab of calcite.  In this case
sizable was looking like it fell between 500 and 1,000 pounds!  Though the
wedges appeared easy to set they were almost impossible to hammer with any
authority.  He had worked himself back under an overhang that only allowed
about two feet of swinging distance.  With our short handled 10 and 12 pound
hammers this hardly allowed for enough force to keep the wedges in place.
I had suggested a more manageable approach but he was not discouraged and
continued to work the fracture.  After about an hour some progress was being
made so we took shifts pounding on the series of eight wedges.  Two hours
after that in the mid day heat we began to hear what we had hoped for. The
initial pops and cracks that told us the slab would soon yield were a
welcome sound compared to the steady clank of hammers on firmly embedded
wedges.

Once the large calcite and wall rock slab had released it just lay there
waiting for the Arm Corp of Engineers to come and move it.  Since our
resources did not include the small army of men that would have been
required to move the block we had to rely on hand tools.  We began by
dividing the slab into more manageable pieces while trying to preserve the
garnet crystals that were peeking out of the calcite on different areas of
the slab.  Once chopped into five or six pieces we removed the chunks from
the depression created by the slabs removal.  These blocks were set aside
for more

careful examination later.  Our real interest was in what lied below and
behind this slab’s initial rest spot.

After crawling back under the ledge I was able to remove several 30 to 50
pound pieces of calcite from a tributary seam that ran perpendicular to the
main calcite vein we had been working.  When sliding out one of these pieces
I immediately noticed a group of crystals dotting its surface.  Once out in
the light of day the questions began.  The crystals were a deep purple in
color, ranged in size from one quarter to one and one quarter inches and had
excellent form, luster and translucence.  No one at the site was able to
venture more than a guess as to their identity.

The following day after a restful night of camping we took the specimen to
geologist, Chris Fouts at the Chamber of Commerce in Bancroft.  Again the
questions were more numerous than the answers.  Scapolite?  Vesuvianite?  
The speculation continued.  It was not until about a week later after
numerous tests and a ultraviolet light examination that the identity was
determined.  They were large, gemmy zircons.  To the knowledge of numerous
authorities familiar with the site they were unique in both their size and
color.  Though zircons are occasionally found at the York River site it is
unheard of to find large ones or colors other than white or sometimes clear.
  These crystals were mostly double terminated and in matrix.  For me they
were one of the best find of the summer.

Needless to say,  Bancroft was the place to be summer collecting so our
trips continued.  In all, July involved no less than four trips to the site
to collect.  Several short fall collecting trips were taken, as well.  The
bugs were thick and the digging difficult, but , the rewards were fabulous.  
It could be seen where others had worked the area with power drills and
saws.  Our arsenal of weapons only included an assortment of hammers, cold
chisels, home made wedges, wood splitting wedges and pry bars.  We would
always work fractures in an attempt to release large blocks of rock at the
calcite and wall rock contact.  The bigger the block the better due to the
fragility of the specimens.  Removing small chunks resulted in nothing
except destroyed garnets.  There was lots of sweat involved in removing
these blocks.  The calcite here seemed to be almost elastic in nature,
absorbing the blows from our steel while seldom yielding.  The use of wedges
made a big difference.  We were able to work a series of wedges below a
slabs and pound them home until something gave.  Often it took hours to
remove a single chunk, but, when done correctly the chunks
were enormous.  One piece was so large it took three men to lift it into the
van.  We were now learning what was involved to recover specimens from this
location.

We also heard someone else had worked the location by dumping acid to
dissolve the calcite.  It was a shock to hear this given the obvious
environmental concerns regarding this form of collecting.  Even when
attempts are made to properly neutralize acid used on- site, no one can
possibly be aware of the potential specimens destroyed by such an act.  It
is nothing short of appalling to think of someone doing this to a highly
fractured rock surface fifty feet from a river!

To summarize our efforts we had removed an enormous amount of material which
was prepared at home.  A few weeks later and many hundreds of dollars in
acid later we had a number of magnificent specimens.  Occasionally, garnets
as large as baseballs were exposed.  Aesthetic mixes of garnet, vesuvianite,
and clinopyroxenes formed some of the best clusters.  We never encountered
another group of the large, purple zircons though we search quite
extensively.  We had heard the zircons were a rarely encountered mineral at
this site, but they were described to us as being very small and clear to
white in color.   The combinations and formations shown by some of the
specimens was also exceptional for this area.  Large, brownish red garnets
perched in beds of forest green clinopyroxenes proved to be especially
attractive.

The clinopyroxene mineral from this location has sometimes been referred to
as diopside.  I have not seen anything in the literature to support this
identification.  The mineral has a even, dark green color, good crystal form
in larger specimens and is usually referred to as clinopyroxene.  For the
most part, this clinopyroxene forms aggregates of thousands of small
intergrown crystals.  When grossular garnets are found in combination with
the clinopyroxene the two minerals are often intergrown with one another.

Zircons were rarely encountered, but several were discovered when going over
the materials with an ultraviolet light.  The zircons from this site
fluoresce a bright yellow in both short and long wave ultraviolet light.  
Often they were small and white in color.  So small the only way they were
noticed at all was by the use of the ultraviolet light.  The vesuvianites
were a walnut brown and in some cases almost black in color.  They exhibited
exceptional crystal form in most cases while occasionally taking on a more
malformed appearance as if they had been partially melted.  In all case they
exhibited a wonderful glassy luster.   When broken their cross sections
revealed that their growth was zoned.  Though one specimen of the
vesuvianite was almost an inch long most were much smaller.  Also found were
cancrinite, biotite, and brucite seldom in specimens worthy of note.

It should be mentioned that approximately thirty minerals are documented as
occurring at this site.  The more common species have already been noted.  
Less common minerals usually occur as irregular patches, veinlets or
disseminated grains:  magnetite, pyrrhotite, graphite, hydrotalcite,
hydromagnesite, olivine, brugnatellite, apatite, wollastonite, and scapolite
are but a few of the diverse mineral species to be found.

When planning a visit to Bancroft rockhounds may want to keep in mind the
annual Rockhound Gemboree.  Bancroft in advertised as the mineral capital of
Canada for good reason.  Dozens of collecting site are located within a
short distance of the town.  The Gemboree is in its 35th year and a major
tourist attraction for this small community.  Thousand come each year to
take part in the buying, selling and trading of the wares related to our
hobby.  Numerous small stores, restaurants, gas stations and businesses
serve the small population of less than 3,000 that live in Bancroft.  A wide
range of accommodations are available for the overnight traveler.  We
frequent the several KOA campground in and surrounding the town.  Others
might prefer the hotels and bed and breakfasts that are happy to serve
visiting rockhounds.

In closing, what initially began as a way to kill some time turned out to be
a productive revisiting to a site I once thought was not worthy of any
serious investigation.  This site is visited hundreds of times annually by
collectors searching for quality garnets.  Through the investment of some
back breaking effort  superb specimens can still be recovered from this
often overlooked site in Ontario, Canada.



Suggested Resources:

Bancroft and District Mineral Collecting Guidebook,  Bancroft & District
Chamber of Commerce, Box 539, Bancroft, Ontario, Canada, KOL 1C0, Phone
(613)332-1513.

Rocks and Minerals For the Collector,  Ann P. Sabina, 1988.  Geologic Survey
of Canada Miscellaneous Report 39, Canadian Government Publishing Centre
Supply and Services Canada, Hull, Quebec, Canada K1A 0S9.



Directions:
Leave Bancroft on highway 28 east and travel 10.9 km and cross the York
River.  Turn onto the first left after crossing the bridge into the parking
area.  The site is approximately 400 meters down the dirt road that travels
downstream (north).  You will see the workings on the hillside immediately
to your right.  Take care if you drive this road.  It is recommended that
you leave your car at the parking area.  Remember that the Chamber of
Commerce periodically does field trips to this location.  Their trips are on
Tuesdays and Thursdays during the months of July and August.  You also have
a the expertise of a professional geologist when using these guided tours.

 

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