Laboratory Manual for Introductory Geology 4e

GEOTOURS EXERCISE 3
Extracting Minerals from the Earth
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Exploring Geology Using Google Earth
1. Visit digital.wwnorton.com/geolabmanual4
2. Go to the Geotours tile to download Google Earth Pro and the accompanying
Geotours exercises file.
Expand the Geotour03 folder in
Google Earth by clicking the triangle to
the left of the folder icon. Check and
double-click the Banded Iron Formation
icon to fly to a position south
of Ishpeming, Michigan. Here, the
placemark shows a large quarry where
Fe-rich minerals are being extracted
from the ground as a source of iron. In
this area, metallic gray Fe-rich minerals
are commonly interbedded with
jasper (red microcrystalline quartz) to
form the beautiful (and often folded)
banded iron formation shown in the
placemark photo.
(a) Dark gray Fe-rich minerals in
banded iron formations typically
are either magnetite (Fe 3
O 4
) or
specular hematite (Fe 2
O 3
). To
differentiate between the two,
recall that color typically isn’t
diagnostic for minerals, but that
streak on unglazed porcelain
tends to be relatively consistent for a given mineral regardless of its color. Specular hematite, like other forms of
hematite, produces a prominent red-brown streak, whereas magnetite typically exhibits a dark gray/black streak.
Check and double-click the zoomable photo labeled Streak. Given the color of the streak in the zoomable photo,
which dark gray Fe-rich mineral is present in the banded iron formation?
Minerals are incredibly valuable in our day-to-day lives. However, their extraction often comes at a price to our
environment (use Google Earth to tour the open pits and waste spoil piles that define the quarry).
(b) Check and double-click the Pit Floor and Pit Rim placemarks. In order to get a sense of scale of these landscape
scars, pause your cursor over each placemark and note their elevations (elev in meters along the bottom right of
the Google Earth viewer window). Which range best describes the depth of this pit (i.e., their difference in
elevation)? Less than 100 m? 100–200 m? 200–300 m? 300–400 m? More than 400 m?
m
(c) Fly back out to a regional perspective. What other ecological impact of mining is prominent in this area?
74 CHAPTER 3 MINERALS