Fifty Point - calcite eyes EarthCache

This cache has been archived.

Geocaching HQ Admin: It has now been over 30 days since Geocaching HQ submitted the disabled log below and, unfortunately, the cache owner has not posted an Owner maintenance log and re-enabled this geocache. As a result, we are now archiving this cache page.

More information in the Help Center.

For locations where new EarthCaches may be permitted, please remember that any cache submission must meet all current EarthCache guidelines and expectations on the Geological Society of America web site and in the Help Center.

More
Hidden : 6/10/2011
Difficulty:
1 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

Join now to view geocache location details. It's free!

Watch

How Geocaching Works
Looking for a different adventure?

Please note Use of geocaching.com services is subject to the terms and conditions in our disclaimer.

Geocache Description:

Part of a series of caches in the Fifty Point Conservation Area.

Information About the Conservation Area
Fifty Point is a beautiful 80-hectare conservation area on the south shore of Lake Ontario. It offers many family picnic areas in a natural setting while providing opportunities for bird watching, boating, camping, fishing, hiking, swimming, and many sporting activities. There are even separate beaches for people and pets! There is a stocked fishing pond (no fishing license required) with a wheelchair accessible fishing dock. For more information, visit the Fifty Point Conservation Area website.

Notes:
  • There is a fee to enter the park.
  • The park is not open at night.
  • The park entrance is at 1479 Baseline Road, Winona, Ontario ( N43° 13.010’ W079° 37.703’).
Geocaching Summary Information About This Cache
Calcite is a common crystalline form of natural calcium carbonate, CaCO3, that is the basic constituent of limestone, marble, and chalk. At this earthcache location you can see how the white, circular calcite deposits in the limestone boulder provide it with “eyes” on you!

The mineral was named in 1849 by the Austrian mineralogist Wilhelm Karl von Hardinger as the German word "calcit" from the Latin word "calx" for "lime".

Compared with other minerals and rocks, calcite is relatively soft. Although its colour can be extremely variable, it is generally white or colourless. However, impurities can sometimes give it light shades of colour. Occasionally, it is iridescent. Its luster can be vitreous to resinous to dull in massive forms. Its crystals can be transparent to translucent.

Calcite, like most carbonates, is very reactive with even weak acids, such as vinegar, and it effervesces readily in dilute hydrochloric acid. In the reaction, calcite (CaCO3) breaks down into calcium (Ca), water (H2O), and carbon dioxide (CO2).

Calcite is intricately tied to carbon dioxide in another way. Because many sea organisms such as corals, algae and diatoms make their shells out of calcite, they absorb carbon dioxide from the sea water by reversing the reaction described previously. This is fortuitous for us, because carbon dioxide contributes to the so-called "green house gas effect". Environmentally, therefore, calcite is very important and may have been quite important to the successful development of our planet. By pulling carbon dioxide out of the sea water, this biological activity allows more of the carbon dioxide in the air to dissolve in the sea water and thus acts as a natural carbon dioxide filter.

Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, acidity, and dissolved ion concentrations. Although calcite is fairly insoluble in cold water, acidity can cause dissolution of calcite and the release of carbon dioxide gas. Calcite exhibits an unusual characteristic, called retrograde solubility, in which it becomes less soluble in water as the temperature increases.

When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. When conditions are right for dissolution, the removal of calcite can dramatically increase the porosity and permeability of the rock. If it continues for a long period of time may, it can result in the formation of caverns with stalagmites and stalactites.

At this location, the calcite has been precipitated from groundwater to fill in hollow voids in the rock. Typically, such voids can be caused by disturbances in the rock such as escaping gas bubbles, shrinkage cracking, or decaying plant roots. Therefore, in geological terms, these are “calcite crystal infilled cavities”. But that explanation is not as nearly as mysterious or magical as calling them “calcite eyes”.

Although calcite is a calcium carbonate mineral, not all calcium carbonate minerals are calcites. Aragonite and vaterite are two other “polymorphs” (or, “many shapes”) that have the same chemistry, but different crystal structures and symmetries. Aragonite is orthorhombic, vaterite is hexagonal, and calcite is trigonal. Aragonite is a common mineral, but is still much less common than calcite which is the more stable mineral at most temperatures and pressures in most environments. Vaterite is extremely scarce and rarely seen.

You can log your visit without prior authorization. However, in order for it to remain you must e-mail the answers to two questions and, for each, indicate the reason for your answer.
  1. Do these calcite eyes contain impurities?
  2. What is the likely cause of the voids in these rocks where the calcite formed?

Additional Hints (No hints available.)



Advertising with Us