Amethyst EarthCache
Hidden : 8/11/2012
Difficulty:
2 out of 5
Terrain:
2.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


Amethyst, a variety of quartz, is the official gemstone of Ontario. Amethyst's relative scarcity worldwide is because it requires a special geological environment for growth: an iron-rich, mineral-bearing liquid saline solution; a high pressure situation; and an appropriate temperature (90 to 250°C). It is also thought that there must also be radiation present for the quartz to form amethyst.

Amethysts often grow in cavities in the earth's crust. Round or oval cavities may be caused by gas bubbles, oval cavities in lava or pockets that occur at the centre of very course grained bodies. These cavities become lined with small crystals near the wall; larger crystals grow at the centre. This formation is called a geode.

Also, faults and fissures in the earth's crust may open because of tectonic movement. Given the right conditions, amethysts may grow in these fault lines and form a vein of amethysts as hot waters and gasses escape from the earth's crust.

The area north of Lake Superior between Thunder Bay and Nipigon has the largest amethyst deposit in North America and the second largest deposit of this gem in the world. However, much of the amethyst in this region is not suitable for high quality cut gemstones. Locally, it is found both in the cavities of volcanic rock and in faults.

The colour of this gemstone varies between pale or almost colourless reddish/violet to dark bluish purple. The colour develops as a result of the quartz crystals forming in the presence of the iron and other minerals.

Amethysts prefer to form in groups of six sided crystals (often, 3 larger sides and three smaller sides) and often show nothing but points or pyramid tops on the surface. Amethysts are very hard, tend to be brittle and are prone to shatter if you try to break them without the right tools (such as a diamond drillbit).

To log this cache, you must go to the site to find amethysts "in the wild." E-mail the cache owner your answers to these questions:
1.) At this location you will see a pit that you can walk into. Estimate the height of the pit at the deepest point.
2.) Describe in your own words the colour of the amethysts you find at this location.
3.) Estimate the size of the majority of the amethyst crystals that you see at this location.
4.) Do you believe the amethyst at this location grew along a fault line or in a cavity? Why?

Though not required to log the cache, I encourage you to take a picture of yourself by some amethyst at this location. To get to this location, I recommend parking at Trowbridge Falls park. The trailhead is on the south side of the parking lot across from the second row of parking.

Please do not remove any rocks or take any samples from the location.

Additional Hints (No hints available.)



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