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Mount Apatite Park, Auburn, Maine
The Mt. Apatite quarries were important producers of commercial feldspar
in the early 1900's. They played a prominent part in Maine's mining history.
During the course of this mining activity, rare minerals and colorful crystals
of green and pink tourmaline were found in both the Greenlaw and Maine
Feldspar Quarries. These quarries also produced many large crystals of
transparent smoky quartz. The complexity of the mineral assemblage at Mt.
Apatite is matched by only a few other localities in Maine.
These quarries are among a small number of mineral collecting sites
in Maine that offer a combination of good public access and the possibility
of finding many different minerals. The ledges and boulders surrounding
the quarry pits show interesting geological features, including basalt
dikes cutting granite pegmatite, and interlayering of pegmatite with metamorphic
rock. The coarse pegmatite shows large, easily visible examples of several
common rock-forming mineral groups such as quartz, feldspar, and mica.
Various features around the quarries illustrate former mining techniques
and the linkages between Maine's geologic and human history.
The top of the ledge next to the park trail between the Greenlaw and
Maine Feldspar Quarries is an excellent place to show the effects of glacial
abrasion. The ledge has been scoured by rock debris dragged along at the
base of the moving glacier, forming a flat and polished surface with striations
and grooves parallel to the flow direction of the ice. Late-glacial marine
sand deposits and dunes composed of windblown sand can be seen at the base
of Mt. Apatite.
|Permission: Mount Apatite Park is owned and administered
by the City of Auburn. It is open to the public, and no special permission
to visit is required. Further information, including a detailed map of
the park and its trail system, is available from the Auburn Parks &
Recreation Department (207-333-6601 X2108).
Location: Town of Auburn in the Minot quadrangle. Abandoned
quarries within the park are located on the southeast side of Mt. Apatite,
north of Route 11/121, between Hatch Road and Garfield Road (see map).
Another group of quarries (Pulsifer, etc.) are located on the west side
of Mt. Apatite, but these are not open to the general public and will not
be discussed here.
Access: Ample parking for cars or buses is available along
park access road. Park next to road, preferably in or near the woods at
the base of the hill (road is gated beyond this point). Check at National
Guard armory if in doubt about where to park buses, since the large field
is armory property. There are no toilet facilities at the quarries.
Group size: Large.
|Exposure: The quarry pits have steep rock walls, and
some of them are flooded (Figure 1). Caution
is necessary in exploring these areas. The big piles of waste rock (dumps)
next to the quarries are good places to find mineral specimens, but be
careful not to roll rocks downhill if people are below you. The remainder
of the park is generally wooded and has a well-developed trail network.
Sampling: Allowed. The park rules state that within the
quarry and dump areas, "it is permitted to use hand tools to explore for
mineral and gem specimens to a depth of two feet." Recommended equipment:
knapsacks or pails, paper for labeling and wrapping mineral samples, sturdy
geologist hammers (or equivalent) for breaking rocks, short-handled shovels
or other tools for digging, safety glasses, first-aid supplies for cuts,
heavy shoes, cameras, food and beverage.
Directions: From junction of Routes 4/100/202 and 11/121
in Auburn, drive west on Rte. 11/121 for 1.9 miles. Turn right onto Garfield
Road and go northwest for 0.50 mile. Turn left onto Stevens Mill Road.
Go to end of this road, pass National Guard armory, and continue on dirt
road across large open field. Park buses next to road on west side of field;
cars and vans can park among trees. Walk uphill, staying on the old quarry
road, for about 0.4 mile. The Greenlaw Quarry and associated dumps are
on the right (north) side of the road; the Maine Feldspar Quarry and dumps
are to the left.
Geology and history
The Mt. Apatite quarries were excavated in a type of igneous rock called
granite pegmatite (often simply called "pegmatite" in Maine). This is a
coarse-grained variety of granite in which the individual mineral grains
are very large. They may be several inches - or even more than a foot -
in diameter. The most abundant minerals in the pegmatite are creamy white
microcline (feldspar), glassy gray to white quartz, and flat sheets of
shiny muscovite (mica). Muscovite is very distinctive because the larger
pieces can be split easily into thin transparent sheets. This property
is called cleavage. It occurs along planes of weakness in the molecular
structure of a mineral. Muscovite and other species of mica have one direction
of excellent cleavage, while the feldspars have two directions of cleavage
(at right angles) which are not always obvious. Quartz lacks cleavage and
breaks along jagged irregular fracture surfaces.
These quarries have a long history of mineral production. They were
operated commercially as a source of feldspar during the early 1900's (Perham,
1987). This mineral is used for making china and other ceramic products.
The feldspar from Mt. Apatite was hauled to a nearby mill built in 1897
at Littlefield Station in Auburn. Here it was ground to a fine powder and
readied for industrial use. Besides the pits themselves, a few other remnants
of quarrying are still visible. From the stone wall next to the entrance
road, you can look down into an old trench cut in the bedrock. This probably
was excavated to drain water from the quarries. Groundwater seeps into
many of the quarries in Maine, and had to be drained or continually pumped
out to keep the workings dry.
|During feldspar mining the quarry workers sometimes encountered rare
and unusual minerals. (The mountain is named after a phosphate mineral
called apatite, which was found as beautiful deep purple crystals at the
Pulsifer Quarry on the west side of the hill. See Figure
2). These minerals might be put aside to be sold to museums and gem
cutters, but in other cases the superintendents discouraged such activities
because they did not want to slow down the mining operation. Crystals of
some minerals such as beryl and garnet were encased within the solid rock.
Other crystals, including quartz and valuable green and pink tourmalines,
were found in cavities in the pegmatite. These "pockets" are natural open
spaces where concentrations of gas or liquids containing rare elements
remained late in the cooling history of the granitic magma. Fine transparent
crystals had the best chance to form in this environment, though they were
often shattered by explosive pressure changes as the rock cooled. King
(2000) provides a detailed history of mining and mineral discoveries at
|Masses of a lilac-colored lithium mica (lepidolite) typically occurred
in the vicinity of tourmaline pockets. You may find pieces of this colorful
mica on the dumps of the Greenlaw Quarry, which are strewn through the
woods on your right as you enter the quarry complex. You will see lots
of shallow holes that mineral collectors have dug in the rock piles. The
Greenlaw dumps are also the most favorable area in which to find traces
of green and blue-green tourmaline (Figure 3),
though collectors have already gathered up most of the obvious pieces.
Black tourmaline (resembling lumps of coal) is more likely to be found,
along with glassy dark-red chunks of garnet and fern-like growths of muscovite
mica. Some of the pegmatite is "graphic granite" in which stringers of
quartz form curious geometric intergrowths with feldspar.
A variety of surficial deposits (unconsolidated sediments which overlie
bedrock over much of Maine) can be seen as you approach the quarries. The
flat cleared area around the armory consists of sand, which is visible
where the ground surface is unvegetated. In the woods west of the field,
there are low mounds which are likewise composed of sand. However, after
the road crosses the small swampy area and starts climbing the hill, the
surface of the hillside is littered with boulders. The probable origins
of these deposits are discussed below.
The granite pegmatite at Mt. Apatite resulted from cooling and crystallization
of a body of magma. This mass of molten rock was enriched in water and
rare elements, giving rise to the variety of rare minerals found in the
quarries. The source of the melts that produced the pegmatite veins in
southwestern Maine continues to be debated: were they offshoots from magma
intrusions that cooled and formed granite bodies such as the Sebago pluton
(igneous model), or did they form when local metamorphic rocks were heated
to the point that partial melting occurred (metamorphic model)? These two
processes are not mutually exclusive, since magma from a distant source
may intrude and melt the surrounding metamorphic rocks, producing locally
derived granitic magma.
According to the traditional igneous model, during the cooling of a
magma of granitic composition, many rare elements tend to concentrate in
the final residual melt because they do not fit well in the structures
of the ordinary rock-forming minerals formed earlier in the crystallization
process. The presence of water both lowers the crystallization temperature
of the melt and facilitates the migration of these elements and their concentration
in the final parcels of magma, which may intrude fractures in adjacent
rocks and finally solidify to form pegmatites.
Mineralogists who study the origin of New England pegmatites are comparing
the chemistry of these rocks with the surrounding host rocks (commonly
metamorphic) and with nearby granite plutons. The pegmatites in the Auburn
area are part of a large swarm (Oxford pegmatite field) concentrated around
the northeast margin of the Sebago pluton (Wise and Francis, 1992). This
suggests a genetic relationship between the granite body and pegmatites.
Creasy (1979) has mapped the bedrock on Mt. Apatite as "heterotextural
granite", a map unit which may include both pegmatite and regular granite
complexly interlayered with metamorphosed sedimentary rocks. He concluded
that the Sebago granite, and presumably the associated pegmatites as well,
were derived from melting of the metamorphic rocks. Thus, Creasy's findings
support the metamorphic model for the origin of the Mt. Apatite rocks.
Simmons et al. (1995, 1996) likewise favor a metamorphic origin for Maine
pegmatites, based on textural and geochemical evidence. Assuming the same
age as the Sebago granite, the pegmatite on Mt. Apatite would have formed
around 293 million years ago, in late Carboniferous time (Tomascak et al.,
The surficial sediments on Mt. Apatite are much younger than the bedrock.
They probably formed during and just after the most recent glaciation,
between about 25,000 and 13,000 years ago (Marvinney and Thompson, 2000).
The bouldery material draping the hillside is rock debris (till) deposited
directly from glacial ice. Till is a more-or-less random mixture of clay,
silt, sand and rock fragments that the ice sheet eroded, transported, and
then redeposited. Large angular boulders scattered across the ground often
indicate the presence of till beneath the surface cover of soil and vegetation.
The effects of glacial erosion are nicely displayed on the large horizontal
ledge surface next to the trail, where it passes between the quarry pits.
During the maximum phase of the last glaciation, the ice flowing across
this area was several thousand feet thick. Sand particles and rock fragments
at the base of the glacier were dragged over the ledge under great pressure,
"sand papering" the rock surface until it was flat and smooth. In this
case the ledge is actually polished - notice how it reflects sunlight when
viewed at certain angles. Individual rocks dragged across the ledge produced
parallel scratches. The narrow ones are called striations, while the deeper
and broader furrows are called grooves. These scratch marks are oriented
from NNW (340 degrees) to SSE (160 degrees), parallel to the flow of the
glacier. By themselves, they do not tell us which way the glacier moved,
but they indicate two possibilities: toward the north-northwest or toward
the south-southeast. From other types of evidence, such as the transport
direction of rocks from known sources, we can safely infer that ice flow
in this part of Maine was generally southward, and 160 degrees is presumed
to have been the direction of ice flow across Mt. Apatite.
As the last glacial ice sheet withdrew from Auburn, areas below about
350 ft in elevation were submerged by the sea. This happened because the
earth's crust was depressed by the weight of the ice. The depression persisted
for a short time after glacial retreat, allowing the sea to extend inland
and flood low-lying areas as the ice margin receded. Fine sediments washed
into the ocean and formed the low flat sand plain seen in the field around
the armory. The direction from which the sand came is not obvious. The
Taylor Pond basin, just north of here, is slightly lower and there is no
apparent source in that direction. The sand is more likely an offshoot
of the sand plain that follows the nearby Little Androscoggin River valley
to the west and south. The elevation of this plain (250-260 ft) is lower
than the upper limit reached by the sea, so the plain probably formed when
the ocean was receding.
When the land was uplifted in early postglacial time, the marine sands
were blown about by the wind and formed the mound-shaped dunes in the woods.
Since the prevailing winds were from the west, some of this sand may have
blown in from the Little Androscoggin River valley.
Suggested itinerary, activities, and discussion questions
After parking at the west edge of the field, examine the sand plain in
the field near the armory (Site 1 on location
map). If this sand was deposited by a flowing stream, what does its fineness
suggest about the stream velocity (fast or slow)? Compare the topography
of the sand plain with the dunes where you enter the woods (Site
2). How do they differ? (Keep in mind that there has been some human
disturbance of the ground in this area.) If the insides of the dunes were
exposed, what characteristics you look for to tell if they were formed
by wind or water?
Walk west on the woods road leading to the quarries. Just beyond a small
wetland (on left), the road starts to climb. Note the boulders on the hillside
(part of the glacial till), in contrast to the sand on the valley floor.
If time permits, examine a few of these boulders and see if they resemble
the rock types exposed in the quarries. Are there any erratic boulders
that were glacially transported from other bedrock source areas?
Continue uphill, staying on the main road until reaching the quarries.
You will come to a short stone wall on the left side of the road (Site
3). From this point is seen a trench that was cut into bedrock during
quarry operations. Perhaps this was done to drain water from the quarry
pits? There are very few buildings or other structures remaining at the
old mine sites in Maine, so it is challenging to try to reconstruct details
of the mining operations from clues that can still be seen. This is the
domain of industrial archaeology. Can you find other evidence of mining
techniques around the quarries, such as drill holes in the rock or support
structures for booms used to hoist the freshly mined feldspar? Some good
historical photos of Mt. Apatite mining have been reproduced by King (2000).
For those interested in mining history worldwide, a useful Web site is
maintained by the Mining
|Just past the stone wall, there is a smooth flat ledge in the clearing
on the right side of the road (Site 4).
This is a great place to see glacially abraded and polished bedrock, with
striations produced by stones dragged across the ledge at the base of the
ice sheet. Although there are many such glacially smoothed ledges in Maine,
weathering has often destroyed the striations on rock surfaces that have
been exposed for a long time. Pegmatite ledges such as this one contain
quartz and other hard minerals that tend to preserve striations better
than crumbly rock types. Sometimes we can reveal striations that are not
immediately evident. Take a hard pencil (H3), pick a very smooth place
on the ledge (on polished quartz or the creamy white feldspar), and rub
the pencil transverse to the visible striations. This is like taking a
charcoal rubbing from a gravestone image. With a little practice and close
scrutiny, you will see that the striations show as white lines in the areas
smudged by the pencil lead (Figure 4). (Hint:
keep a sharpener handy!) Geologists often use this technique on smooth
ledges where the striations are not so obvious as they are here.
|The group of pits on the north (right) side of the road are the Greenlaw
Quarry. The single large pit to the south is the Maine Feldspar Quarry
(Site 5). Walk down to the water's edge
in the Maine Feldspar Quarry and look across to the high west wall. This
face shows metamorphic rock overlying lighter-colored pegmatite (Figure
Continuing up the road between the quarries brings you to a set of
stone steps. Just to the right of these steps is a low rock face that at
first resembles a stone wall (Site 6; Figure
6). Look closer at this densely fractured bedrock, and you'll see that
it's a dark, fine-grained rock called basalt. The basalt forms a vertical
vein crosscutting the surrounding pegmatite, with a trend of 055 degrees
(NE). Igneous rock veins such as this one are called dikes. Looking closely
at the dike, remnants of pegmatite are still attached to the side facing
you. Compare the grain size of the basalt with the pegmatite. What does
this suggest about cooling rates in the two magma bodies? Which is younger,
or did they crystallize at the same time?
Note that the stone steps have been imported from somewhere outside
the quarry. They are made of fine-grained gray granite and have drill holes
on the edges. These granite slabs look like the foundation stones of many
older houses and barns in the area, and may have come from a former home
site. Farmers in southern Maine often exploited local granite ledges, or
even large boulders, to obtain foundation stone. They took advantage of
natural fractures in the rock to facilitate breaking off the slabs. Drill
holes in hilltop ledges are evidence of this activity.
Climb the steps to a viewpoint on the north side of the road. This overlooks
another old quarry pit which is mostly dry. Look at the boulders placed
next to the pit rim. One of them shows a black basalt dike cutting through
pegmatite. The margin of the dike shows very fine-grained texture due to
chilling in contact with the adjacent rock. Are there any other rock types
among the boulders here?
Return back down the road, past the rock wall, and turn left to visit
the rock piles next to the Greenlaw Quarry (Site
7; Figure 7). This is a good area to gather
a collection of minerals for yourself or your school. Unknown minerals
can be brought home and researched with the help of mineral identification
guidebooks. Keep in mind that the photographs in many nature guides tend
to show ideal or beautifully crystallized minerals, which unfortunately
are not typical of what we usually find!
The common minerals at the Greenlaw are described above. They include
milky and smoky quartz, feldspar species (microcline and albite), muscovite
mica, black tourmaline, and garnet. Two other micas - black biotite and
purple lepidolite - can be found, along with fragments or small crystals
of green and blue tourmaline. You may be lucky and also find some of the
many rarer minerals that have been discovered here. To access another collecting
site, continue back down the road and turn right (south) to the huge dump
pile from the Maine Feldspar Quarry (Site 8;
Figure 8). Many garnets are found here. Thompson
et al. (1998) list 39 mineral species that have been reported from the
Greenlaw and Maine Feldspar Quarries.
at exhibits in museums, and at shows and stores where minerals are sold,
is a good way to get acquainted with them. Students may find that an interest
in minerals leads to a career in the earth sciences or a satisfying lifelong
hobby. Local mineral clubs conduct meetings and field trips, and club members
are usually very helpful to beginners wishing to learn more about the hobby
and mineral recognition. For information on the Federation of Maine Mineral
and Gem Clubs, contact Scott Davidson (Pres.) at (207) 933-3517.
Prof. William B. Simmons (Department of Geology and Geophysics, University
of New Orleans) reviewed the text and provided helpful comments on the
origin of pegmatites. We are especially grateful to the City of Auburn
for keeping this important Maine mineral locality open to the public.
Creasy, J. W., 1979, Reconnaissance bedrock geology of the Poland quadrangle,
Maine: Augusta, Maine Geological Survey, Open-File No. 79-15, 18 p. and
King, V. T., 2000, Selected history of Maine mining and minerals, in
King, V. T., ed., Mineralogy of
Maine, Volume 2: Mining history, gems, and geology: Augusta, Maine
Geological Survey, p. 17-254.
Marvinney, R. G., and Thompson, W. B., 2000, A geologic history of Maine,
in King, V. T., ed., Mineralogy
of Maine, Volume 2: Mining history, gems, and geology: Augusta, Maine
Geological Survey, p. 1-8.
Perham, J. C., 1987, Maine's treasure chest - gems and minerals of Oxford
County: West Paris, Maine, Quicksilver Publications, 269 p.
Simmons, W. B., Foord, E. E., Falster, A. U., and King, V. T. ,1995,
Evidence for an anatectic origin of granitic pegmatites, western Maine,
USA: Geological Society of America, Abstracts with Programs, v. 27, no.
6, p. A411.
Simmons, W. B., Foord, E. E., and Falster, A. U., 1996, Anatectic origin
of granitic pegmatites, western Maine, USA: GAC-MAC Annual meeting, Winnipeg,
Abstracts with Programs.
Thompson, W. B., Joyner, D. L., Woodman, R. G., and King, V. T., 1998,
A collector's guide to Maine mineral
localities: Augusta, Maine Geological Survey, Bulletin 41 (3rd ed.),
Tomascak, P. B., Krogstad, E. J., and Walker, R. J., 1996, U-Pb monazite
geochronology of granitic rocks from Maine: implications for late Paleozoic
tectonics in the northern Appalachians: Journal of Geology, v. 104, p.
Wise, M. A., and Francis, C. A., 1992, Distribution, classification
and geological setting of granitic pegmatites in Maine: Northeastern Geology,
v. 14, no. 2&3, p. 82-93.
Originally published on the web as the January 2001 Site of the Month.
Last updated on January 3, 2012