This week we will investigate the weathering behaviour of several rock types under typical New England weathering conditions.  Before you go over to the graveyard on Zion Street you might find it useful to review the chapter on weathering in the textbook.  

A good place to study the effects of weathering are graveyards, especially graveyards that have been around for a while.  They tend to display a variety of rock types, with the added benefit that most specimen are also clearly labeled, and you can tell for how long they have been exposed to the elements.  During your stay in the graveyard, please be respectful to the place and do no damage!

For this homework assignment you have to go to the graveyard on Zion St., just North of campus.  This is an exercise best done in groups and in broad daylight.  We are trying to study rocks, not ghosts!  For a topographic map of the cemetery click here.
You will notice several major rock types that are used in headstones.  Some are made up from a dense speckled gray rock (Fig. 1.1), others are made from a white, rather homogenous rock (Fig. 1.2), while many of the older graves use a reddish brown stone (Fig. 1.3).

Fig. 1.1	Fig. 1.2	Fig. 1.3

By now you should be able to identify at least two of these rock types.  While walking across the graveyard, notice which rock types tend to hold up well to the weathering process and which ones are easily weathered.  Walk over to the western side of the graveyard and stay on the hill.  You will find a section of graves, many of them marked with obelisks as shown in the image at the bottom of the base.  Find a few old graves that are marked by obelisks of comparable age (you should have no problem finding several graves from the early 19th century).  Make sure that you pick a representative sample.  You should look for an approximately equal number of white and brown obelisks.

The white rock is marble, which is probably brought in from NE Connecticut, the brown rock is a sandstone quarried locally.  In this exercise you will study the weathering behavior of both rock types and compare it to the weathering behavior of igneous rock surfaces of similar age.

1.    Start out with the obelisks made from sandstone.  What are the effects of weathering on the stones?  Do you recognize a certain pattern of damage?  How might the weathering of these rocks relate to the type and texture of the rock?  Which processs do you think cause this particular weathering pattern?

2.    Next study some of the obelisks made from marble.  Do you see the same type of damage on the monuments?  Are they more or less severely weathered than their sandstone counterparts?  Which type of stone has more structural integrity, which one is better in preserving the details of the stone carving?  Which process might be responsible for the weathering effects seen in marble?  (Hint, marble is 100% CaCO₃ - how do you test for calcite? - No, leave your acid bottle at home!  No vandalizing the graves, please!)

3.    Finally, find a headstone of comparable age that is made from igneous rock.  What can you say about the relative weathering rates of igneous rocks, with respect to the other two rock types? Can you describe the rock and identify its mineral components? After studying its composition, can you come up with a name for it?  Fig. 4.28 might be an excellent tool, helping you to decide this question.