Calcite - Three Episodes - in the Mines and Deposits within the Herkimer Mining District
Calcite is the last major crystal forming event in the Herkimer Mining District, and occurs in three stages. The early
stages resemble the calcite found within fracture seams in Amsterdam, NY. The latter stages show similarities to
the calcite found around Illion, NY. Overlap of these stages (later on top of earlier) can be found wtihin the district.
Click on the button next - to go to weathering page
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Calcite is rarely found without
some element of weathering
effect. This will be seen is
some of the photos in the
accompanying slide show
here, but more dramatically
illustrated on the weathering
page (click button above).
The slide show here seeks to
present the best examples.
The most common form that
calcite takes in the district is
as flattened “nails head”
crystals. These are called
this because from the side
view they can look like the
head of a nail. The calcite can
occur as single disk like
crystals up to 120 cm but
more commonly average in
the range of 3 to 5 cm. It is
also quite common for these
disc like crystals to stack next
to each other in parallel
growth. This calcite is most
commonly amber, or honey,
but it can be grey.
The “nails head” form can
also occur with the side
prismatic faces elongated -
and this shows some variation
across the district.
Stage 1 calcite can be found coated with either a layer of white calcite without form, or coated by white to clear calcite
rhombs (like skewed cubes). These white/clear rhombs are commonly small, ranging from 1 to 5 mm across. Occasionally
the crystals will be honey or deep amber and rarely the crystals can occur in a scalenohedral form.
The final calcite stage is boytroidal, masses of rounded mounds. In places the form can appear as stacked mounds. The
color ranges from white/grey to honey yellow. Both crystal forms of stages 2 and 3 can be found in Illion, NY. as well.
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by W. David Hoisington, Ph. D. unless another author/photographer is cited.
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