Holy Zinc EarthCache

History of Zinc

Centuries before zinc was discovered in the metallic form, its ores were used for making brass, and zinc compounds were used for healing wounds and sore eyes. Brass was produced by the Romans in the time of Augustus (20 B.C. - 14 A.D.). By 1374, zinc was recognized in India as a new metal and at Zawar, India, both zinc metal and zinc oxide were produced from the 12th to the 16th century. From India, zinc manufacture moved to China in the 17th century. Zinc was recognized as a separate metal in Europe in 1546. In 1743, the first European zinc smelter was established at Bristol in the United Kingdom.

The Geology

     Zinc makes up about 75 ppm (0.0075%) of Earth's crust, making it the 24th most abundant element. Soil contains 5–770 ppm of zinc with an average of 64 ppm. Seawater has only 30 ppb zinc and the atmosphere contains 0.1–4 µg/m3.

     The element is normally found in association with other base metals such as copper and lead in ores. Zinc is a chalcophile, meaning the element has a low affinity for oxides and prefers to bond with sulfides. Chalcophiles formed as the crust solidified under the reducing conditions of the early Earth's atmosphere.  Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.

     Other minerals from which zinc is extracted include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate). With the exception of wurtzite, all these other minerals were formed as a result of weathering processes on the primordial zinc sulfides.

     Identified world zinc resources total about 1.9 billion tonnes. Large deposits are in Australia, Canada and the United States with the largest reserves in Iran. At the current rate of consumption, one source has estimated these reserves could be depleted sometime between 2027 and 2055. About 346 million tonnes have been extracted throughout history to 2002, and one estimate found that about 109 million tonnes of that remains in use.

Using Zinc as tombstones

     In the mid-1800s the Industrial Revolution was at full speed.  M. A. Richardson and C. J. Willard came up with a new way to capitalize on the new factory system and the Victorian mourning traditions of the time.  In 1873, Richardson began inventing monuments made of zinc.  Unable to get enough capital, he sold out and the Monumental Bronze Company started officially in 1879.  The idea was simple.  Prefabricate most of the monument, and then just fill in names and dates and other personalization to get the customers what they wanted.  They were easier to construct than traditional stone monuments, as well as, cheaper to produce and ship.  Sales hit their peak in the 1880s.  Some people however, thought the monuments cheap imitations and banned them.  By WWI, production was shut down as all zinc was needed for the war effort. 

     To construct the monument a mold was constructed just like for granite or marble monuments.  After the mold was finished, the zinc was heated beyond its melting point to ensure a better fuse then traditional soldering.  The monument was then sandblasted and chemically oxidized to resemble granite and receive its bluish cast.  When exposed to the carbon dioxide (CO₂ ) in the atmosphere, zinc naturally covers itself in a layer of zinc carbonate  Zn₅(OH)₆(CO₃)_2.  This prevents further reaction with air and water. Strong acids, or even acid rain, however will still trigger a chemical reaction.

     One problem that cemeteries has is weathering of stones or the breakdown of rock in situ, that is without moving, and should not to be confused with erosion.   Traditional stones are made of granite, limestone, or marble.  Marble tends to be a very soft stone and weathers quickly.  Granite tends to take a while longer, but still fades over time.  Limestone is affected by acid rain but will last rather a long time. Weathering is caused by the elements like rain and ice, or even biological means like lichens and ivy.  Weathering varies by location based on a host of variables, but a study in Yorkshire, England found that the average marble stone became difficult to read after 70-80 years while igneous rocks, like granite, lasted up to 100-150 years in comparison. 

     One weakness that has damaged these zinc monuments is caused by the pressure from their own weight. Zinc has a tendency to creep, or bend when it's exposed to pressure over time.  This creeping action may also cause tiny cracks on some of the monuments. Obviously, smaller markers do not exhibit this problem.  Proper seating/mounting on concrete bases was important to reduce creep & corrosion from prolonged contact with the soils.

     There are a number of factors that can cause this creeping including the height and weight of a monument, and the sturdiness of the base where it contacts the ground. Proper seating on a solid base, ideally concrete, was important to reduce the creep and prevent corrosion from prolonged contact with the soils. Annual freezing and thawing of the ground can also cause shifting of the base of the monument unless it is on a solid or permanent base.

     In an attempt to boost sales, the Monumental Bronze Company changed the "finish" on the metal base so it would resemble stone. The sandblasting roughened the surface and speed up the natural formation of protective oxide coating. Many pre 1879 monuments are smooth with a grayish colour while the post 1879 monuments have rough surface and are more bluish-silver in colour.

     The company ceased to cast memorials in 1914 when the plant was taken over by the U.S. Government for the wartime manufacture of gun mounts and munitions. The company officially ceased to exist in 1939 however company secretary C.A. Baldwin continued to cast the interchangeable name plates for existing memorials.

To log this EarthCache:

To successfully accomplish the requirements for this Earthcache, please answer the following questions.Pictures are always welcome but they are optional. There is no need to contact me for confirmation before logging this cache but the information should be sent in, either via email or the message system on geocaching.com, in a timely manner. Should there be any difficulty, I will contact you.     

1. What is the one very unique feature of all the zinc monuments? (See hint)

2. Is it pre, or post 1879? Besides looking at the date, is there another way to tell?

3.  Is there evidence of creeping or stress on the base or at one of the other horizontal base sections? While many stone monuments are titled, how does this one look after so many years?

4. Compare the weathering of the white bronze monument to those around it. In terms of readability and resistance to lichens and discolorations, which markers are holding up the best?

5. How long do you think that zinc monuments might last in comparison to other monuments in the area?  Why do you feel this way?

6. Who does this particular monument recognize?

Send me your answers to my profile. Do not post your answers on in your log. If you enjoyed this particular earthcache, you'll also enjoy Ohio Rider's GC7E9AB and GC7E97H. Happy caching!