Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find. At this location, you will be observing a phenomenon called Augen - small eye-like pockets of crystals in the basalt rocks that make up this beach.
Please note: This cache can only be completed at half to low tide. If you come during high tide, you will not be able to see the Augen in the basalt rocks and you will not be able to access the area. Please plan your visit accordingly - you can find information on tides HERE.
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
Questions to answer:
1. Observation & Description: Find a basalt rock with pink augen in it as you wander along the beach. Describe the augen - what is the shape and size, colour, and texture. Can you see the crystals formed within the augen?
2. Geological Thinking: Based on what you see, do you think this augen formed during the original lava cooling or from later mineral growth? Why?
3. Mineral Comparison: Look for another mineral in a basalt rock nearby—perhaps white quartz or green chlorite—and describe where it appears in relation to the augen. Is there more of the pink augen, or of the other mineral(s)?
4. Photo Requirement: Take a photo of yourself (or just your GPS device, or your geocaching name on a piece of paper, or your signature item, a thumbs up) helding a piece of the basalt with pink augen visible. You are not required to show your face in the photo, but each geocacher should upload an image with their log indicating that they were there. You are also welcome to share other photos of your visit to this beautiful area, but at least once image should show you holding a piece of the Augen.
Earth Science Lesson:
Welcome to the stunning shores of the Bay of Fundy, home to the world's highest tides—and a remarkable geological secret hidden within its ancient lava flows. If you explore the basalt cliffs and boulders revealed at low tide, you may notice something curious: large, pink, eye-shaped mineral inclusions set within the dark volcanic rock. These are called augen—a German word meaning “eyes”—and they offer a window into both the region's explosive volcanic past and the powerful geological forces that shaped Atlantic Canada.
This EarthCache highlights the interaction between igneous processes (volcanic basalt flows), mineral crystallization (feldspar augen), and post-volcanic alteration (hydrothermal and metamorphic processes). It offers a rare chance to observe large mineral inclusions in basalt—a setting where fine-grained textures are far more typical.
What Are Augen?
In geology, "augen" refers to large, lenticular (lens-shaped or eye-shaped) mineral grains that form in metamorphic or igneous rocks. In the Bay of Fundy, these augen appear in ancient basaltic lava flows, which erupted during the Late Triassic to Early Jurassic period (about 200 million years ago), when the supercontinent Pangaea was breaking apart.
These augen formed when minerals began to crystallize in pockets within the slowly cooling basalt lava. Over time, tectonic stress and chemical changes caused the minerals to grow in distinctive, oval shapes. The surrounding basalt often exhibits signs of strain or foliation, further accentuating the "eye-like" appearance of these inclusions.
What Makes Them Pink?
The pink coloration of these augen is primarily due to feldspar, especially potassium feldspar (orthoclase or microcline), which commonly crystallizes in volcanic rocks. Feldspar can develop pink, salmon, or flesh tones due to trace amounts of iron, manganese, or microscopic inclusions of hematite.
While feldspar is common in many igneous rocks, its prominence and large crystal size in these Fundy basalts is unusual. The presence of pink augen suggests localized conditions—such as slower cooling, alteration by hydrothermal fluids, or recrystallization under pressure—that allowed the feldspar to grow unusually large and pigmented.
Why Are They Common Here?
The Bay of Fundy sits atop part of the North Mountain Basalt, a massive volcanic formation created during the rifting of Pangaea. These extensive lava flows were among the largest in Earth's history and created thick, layered sequences of basaltic rock.
Several factors make augen more common here than in most basalt flows:
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Slow cooling pockets: The thick, insulated lava flows of the North Mountain cooled unevenly, allowing feldspar and other minerals time to grow larger than usual.
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Hydrothermal activity: After eruption, hot fluids moved through fractures in the cooling lava, supplying minerals and altering the original rock chemistry.
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Tectonic forces: Regional metamorphism and shearing may have helped stretch and shape the feldspar crystals into eye-shaped augen.
Together, these conditions created the perfect environment for augen formation—an unusual feature for volcanic basalt, which normally cools too quickly to allow large crystals to form.
What Other Minerals Might You See?
Alongside feldspar augen, visitors might spot:
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Quartz – clear to milky white; often found filling cavities or lining fractures.
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Chlorite – a greenish mineral often forming from alteration of basalt.
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Zeolites – such as stilbite or heulandite, which can occur in vesicles (gas bubbles) within basalt.
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Hematite – iron oxide that can appear reddish and may contribute to feldspar coloration.
Sources:
MacDonald, A.S., and Barr, S.M. (1988). "Petrochemistry of the North Mountain Basalt, Nova Scotia." Geological Survey of Canada, Open File Report.
The Geological History of the Bay of Fundy
Feldspar Mineral Identification