ST PANCRAS GARDENS – ROCK TYPES
TEACHER’S GUIDE
This guide provides answers to the questions posed in the pupil’s worksheet and
also offers suggestions for future work back in the classroom or as individual
projects for students.
1 LIMESTONE
Before beginning, ensure that pupils have the following:
Map of St Pancras Gardens
Two sheets of fossils
Two colouring pencils
There are two distinctly different types of limestone within the gardens –
Portland Limestone and Carboniferous Limestone. Each one contains a unique
group of fossils that can be used to identify it. You have been given two sheets
of paper that list some of the fossils found in each.
A number of unshaded gravestones are also marked on your map. These are
made of either one of the two limestones. Locate these gravestones and try to
determine their lithology (rock type) by finding as many of the listed fossils in
each one as you can.
Choose a different colour for each type of limestone and colour in the unshaded
gravestones on your map according to your findings. Don’t forget to colour in
your key too!
LOOK at the fossils carefully. Draw what you see and label any features you can
using the sketches provided.
THINK about what you are looking at…
What do these fossilized creatures remind you of? Where do you think they
might have lived? (answer on your notes pages)
They look like shells that you find on the beach. This suggests that they once
lived in the sea.
What does this tell you about how the limestones were formed?
(answer on your notes pages)
The limestones were formed by the deposition and consolidation of fossilized
creatures like those seen here.
2 MARBLE
Marbles are limestones that have been altered by high temperatures and/or
pressures. This process is known as METAMORPHISM, and marble is a
METAMORPHIC rock.
There are a few examples of marble within St Pancras Gardens, but don’t be
misled by the information plaques on some of the memorials because the word
marble is used by stonemasons to mean any rock that can take a polish, which is
not the same definition as a geologist would give!
Compare the marble of the Tate Family Grave with the limestone of the Ann
Abbey Memorial (see map).
How are they similar? How are they different?
Colour (try to find relatively clean surfaces)
________________________________________________________________
___Both are creamy white in colour, but the limestone has a more grey
appearance than the marble_________________________________________
Fossil content (don’t try and identify anything, just look at numbers!)
________________________________________________________________
___The limestone grave has distinct bands of fossils running horizontally across
it, whereas the marble grave has no visible fossils at all____________________
Surface weathering (which has a rougher, more eroded-looking surface?)
________________________________________________________________
___The limestone Ann Abbey Memorial has a much rougher surface where it has
been eroded unevenly. The marble is much smoother______________________
Texture (are they smooth? rough? crystalline? grainy?)
________________________________________________________________
___The limestone is quite rough and visibly grainy. The marble is much
smoother and has a crystalline texture__________________________________
3 GRANITE
What type of rock is granite?
(circle correct answer)
SEDIMENTARY
IGNEOUS
METAMORPHIC
Mineralogy
Quartz is otherwise known as SILICON DIOXIDE.
What is its chemical formula? _____SiO2______
Grain size
Using a ruler, measure the lengths of 5 feldspar crystals (use feldspar crystals
because they have the most regular shape and distinct long axes that can be
easily compared):
Length of feldspar crystal:
1 ___________
Average:
2 ___________
 _____ + _____ + _____ + _____ + _____ 


5
3 ___________
4 ___________
5 ___________
= _____mm
From your average feldspar crystal length, do you think this is a coarse, medium
or fine grained rock? Why?
_______________Granites are coarse grained because the crystals grew slowly
from the melt as an intrusive rock, whereas an extrusive rock, e.g. a basalt
would be fine grained because it cooled more quickly_______________
Xenoliths
Can you see any patches within the granite that look different from the
surrounding rock? (If you are at the Rhodes Family Grave you may not, so try
one of the other granite stones marked on your map).
What distinguishes them from the rest of the granite?
______________They are darker in colour and finer grained________________
What shape are they?
___________They are irregular in shape and rounded at the edges___________
(Check that it is not dirt or lichen that you are looking at!)
These are XENOLITHS (Greek word for “strange rock”). Xenoliths are blocks of
country rock (the rock into which the granite would have been intruded when
molten) that were dislodged by the intrusion and “fell” into the hot magma.
Originally the blocks would have been angular in shape but became more
rounded as they were eroded by the hot magma (i.e. the edges melted).
Draw an example of a xenolith, noting its size and its rounded edges. Try to
point out how it is different from the surrounding granite, but don’t worry about
its mineral content!
XENOLITH SKETCH
4 SANDSTONE
Sandstone is formed by the cementing together of grains of sand. Does this
make it sedimentary, igneous or metamorphic? ______Sedimentary_______
Would you say that this sandstone is coarse grained, medium grained or fine
grained? (use the same criteria that you did for granite)
_________Medium grained___________
Make your way to William Jones’ gravestone (see map)…
This gravestone has very well defined bedding planes.
(Bedding = a series of visible layers in a rock that reflect the original surfaces of
deposition)
Has the gravestone been cut parallel or
perpendicular to these bedding planes?
______Parallel to the bedding planes______
Weathering tends to concentrate along the planes of
weakness between sandstone layers (bedding planes).
As a result, large flakes of sandstone are detached
from the surface, leaving it very uneven.
Bedding
planes
Ασκδϕφησαδη;ασηγ;οηα
σδγηοασηγ ασα;σοδφηαο
σηδα σδγ ηγασηγησ αδ η
σαγ ηασοδγη ασοιηγ ηγ ο
αησ οσηδγ ασηγ ασιηδγο
ηασ γηασγ αση σσηγοαη
σδη αοσιδαοσηδγησγ ιηα
αακσδϕηφασυηδ ασδγηα
σοδηγοιασδγη αισηγδιοη
ασγ οασδηγιοαησγιοηαα
Make a sketch of the whole gravestone, marking on the bedding planes and
eroded surfaces:
GRAVESTONE SKETCH
Eroded surfaces
Bedding planes
Don’t forget
to add a
scale!
And finally…
Using your map, make your way to the Burdett-Coutts Memorial Sundial. Then
complete the diagram using terms from the list below:
PINK GRANITE
MANSFIELD SANDSTONE
MARBLE
PORTLAND LIMESTONE
GREY GRANITE
CAST IRON
GREY GRANITE
PINK GRANITE
CAST IRON
MARBLE
RED MANSFIELD
SANDSTONE
PORTLAND
LIMESTONE
KEY
Portland Limestone
Carboniferous Limestone
St Pancras
Hospital
Railway
William Jones’ Grave
(SANDSTONE)
Soane
Mausoleum
(LIMESTONE &
MARBLE)
Flaxman Family Vault
(LIMESTONE)
Jane Grundy
Memorial
(PINK
GRANITE)
Burdett
Coutts
Sundial
Tate Family
Grave
(MARBLE)
St Pancras Hospital
The
Hardy
Tree
Drinking
fountain
Portland Lst
Carboniferous Lst
Ann & William
Birch’s Grave
(GREY GRANITE)
Ann Abbey Portland Lst
Memorial
(LIMESTONE)
St
Pancras
Old
Church
Portland base &
Carboniferous lid
Rhodes Family Grave
(PINK & GREY GRANITE)