Our rock garden was named in honor of Bud Wobus, Edna McConnell Clark Professor of Geology, Emeritus, in honor of his fifty-five years of service to the college. The rock garden includes boulders and large specimens gathered from across the country: as far away as Washington state and as close as the very site the garden is built on. Highlights of the garden include a 6-foot long petrified wood bench from Arizona and a cut-and-polished block of banded iron formation from Minnesota. Please see below for photos and detailed descriptions of the specimens. Specimens are listed here from north to south along the west side of the building (downhill along Hoxsey Street), and from west to east along the south side of the building (away from Hoxsey Street, past the stone table).
Stockbridge Marble
Rock type: Metamorphic
Age: Ordovician (485 to 444 million years old)
Locality: Williamstown, MA
This rock was excavated during the construction of Wachenheim Science Center; it is a piece of the bedrock that underlies the building. It formed in a similar way to the large, white boulder from the same Stockbridge formation closer to the building; both were originally limestone in shallow sea and were later buried and metamorphosed into marble. The main difference between the two rocks is their mineral content. The white boulder is nearly pure calcite, or calcium carbonate. This stone is composed of the mineral dolomite, a calcium-magnesium carbonate.
Mylonite
Rock type: Metamorphic
Age: unknown
Locality: Western Massachusetts
A mylonite is a rock deformed by intense recrystallization in a deep fault zone under high temperature and pressure conditions. This rock contains quartz, feldspar and mica, and was likely 15 to 20 kilometers below the surface during deformation.
Hawley Formation Crowsfoot Schist
Rock type: Metamorphic
Age: Ordovician (475 million years)
Locality: Franklin County, MA
The Hawley Formation is a highly variable rock unit mainly made up of the metamorphic rock schist. This schist originated as layered muddy sediment that was heated and pressurized at depth so that new minerals grew. This specimen is informally known as “crowsfoot” for the groups of long, green amphibole crystals that resemble birds’ feet.
Stockbridge Marble
Rock type: Metamorphic
Age: Ordovician (485 to 444 million years old)
Locality: Adams, MA
This rock was originally deposited as limestone in a shallow tropical sea, similar to the modern Caribbean. The limestone was buried to several kilometers depth during the building of the Appalachian mountains, where it recrystallized due to heat and pressure – a process known as metamorphism – which caused the growth of larger calcite crystals, giving the marble its characteristic sugary look.
This specimen was generously donated by Specialty Minerals, Inc.
Goshen Formation Schist
Rock type: Metamorphic
Age: Lower Devonian (410 to 406 million years)
Locality: Franklin County, MA
The Goshen Formation is a highly variable rock unit mainly made up of the metamorphic rock schist. This schist originated as layered muddy sediment that was heated and pressurized at depth so that new minerals grew. This specimen contains abundant mica, which gives the stone its shiny luster and silver-gray appearance. These rocks are quarried for decorative construction stone, and were widely used inside Wachenheim Science Center and for the large table by the southwest entrance to the building.
Sugarloaf Formation (Arkosic Conglomerate)
Rock type: Sedimentary
Age: Late Triassic – Early Jurassic (approx. 237-174 million years old)
Locality: Greenfield, MA
Arkose is a type of sandstone that contains abundant mica and feldspar grains. Conglomerates are sedimentary rocks that contain pebbles and cobbles as well as sand. The Sugarloaf Formation was deposited by streams flowing into a basin that formed as tectonic forces within the Earth began to pull apart the ancient supercontinent of Pangea, a process known as continental rifting. Streams flowed into the basin, depositing conglomerates and sandstones as well as other sedimentary rocks. That ancient basin is now a part of the Connecticut River valley. Some of these rocks also contain dinosaur trackways, such as those in the basement level of this building.
Gore Mountain Garnet Amphibolite
Rock type: Metamorphic
Age: Mesoproterozoic (1 billion years)
Locality: Ruby Mountain, Indian Lake, NY
The Gore Mountain Amphibolite is notable for its very large, deep red crystals of garnet, some of which can reach three feet across. The amphibolite formed by metamorphism that occurred about 1 billion years ago, during an ancient mountain-building event known as the Grenville Orogeny. Metamorphism took place at very high temperatures (as high as 900 °C) and high pressure (10GPa, or about 30 km deep in the crust). The large size of the garnet crystals is attributed to fluids percolating through the rock during metamorphism, which aids the diffusion of atoms and enables the growth of large mineral grains.
The specimen was generously donated by BARTON International.
Hamilton Group Fossiliferous limestone
Rock type: Sedimentary
Age: Middle Devonian (393 to 383 million years)
Locality: Albany County, NY
This limestone was formed when much of Upstate New York was a shallow sea filled with marine animals, mostly invertebrates such as corals and other kinds of marine shelled creatures. This specific stone is covered in the fossils of brachiopods, marine invertebrates that look similar to clams, but are in fact in a separate phylum. Brachiopods were extremely diverse and abundant in Devonian seas, and while some are still alive today, they are much less common.
Silver Plume Granite
Rock type: Igneous
Age: Mesoproterozoic (1.4 billion years)
Locality: Fremont County, CO
Pink granites ranging in age from 1.8 to 1.0 billion years are common along the Colorado Front Range. Though similar in appearance, many of these rocks have quite different origins and mineral content. The Silver Plume granite began as magma (molten rock) deep in the earth’s crust, rising to a depth of approximately 6 to 10 km before it cooled and crystallized.
This specimen was generously donated by THE Aggregate Source.
Rock type: Sedimentary
Age: Upper Triassic (approx. 225 million years)
Locality: Apache County, AZ
The process of petrification (literally: making into rock) preserves original biological textures in extraordinary detail, if the conditions are just right. Shortly after the original tree died, a volcanic eruption buried the tree in ash. Warm groundwater flowing through the ash dissolved silica, and then seeped into the buried wood, slowly replacing the log’s original organic matter with the silica, which hardened to form the silica mineral jasper. This petrified log was recovered on private land near Petrified Forest National Park in 2005.
Columbia River Basalt
Rock type: Igneous
Age: Miocene (16.7 to 5.5 million years)
Locality: Oregon
The shape of this specimen is fully natural. Basalt forms when liquid lava cools and solidifies. Lava contracts as it cools, forming cracks in regular, polygonal patterns that create prismatic columns. The pattern is often referred to as “columnar jointing”. This specimen is an example of a single column of Columbia River Basalt. The lava that formed Columbia River Basalt flowed hundreds of kilometers, spilling across Oregon and Washington, western Idaho and northern Nevada before cooling and solidifying. Other famous examples of columnar basalt include Devils Postpile in California and Giant’s Causeway in Northern Ireland.
Animikie Group (Banded Iron Formation)
Rock type: Sedimentary
Age: Paleoproterozoic (1.8-1.9 billion years)
Locality: St. Louis County, MN
Banded iron formations (or BIF) are unusual rocks that formed early in Earth’s history, when the chemistry of the atmosphere and ocean contained very little free oxygen. They were deposited in deep water, and their alternating thin layers of iron oxides (similar to rust) and chert (a fine-grained variety of quartz) likely record periodic changes in ocean conditions Because the iron minerals in BIF are oxidized, we know that free oxygen – a product of photosynthesis – was present in at least small amounts in Earth’s early oceans.
Caledonia Granite
Rock type: Igneous
Age: Mesoproterozoic (1.1 billion years old)
Locality: Rivière à Pierre, Quebec, Canada
The gray stone that comprises the base of Wachenheim Science Center is called Caledonia Granite. Caledonia Granite is quarried in southern Quebec and is a common dimension stone used in buildings and countertops.
Formed during an ancient mountain-building event known as the Grenville Orogeny, the Caledonia Granite contains abundant microcline feldspar (pink, angular grains), quartz (clear or translucent gray grains) and pyroxene (black grains). The potassium-rich microcline feldspar grains also contain microscopic intergrowths of sodium-rich plagioclase feldspar, which are, of course, not visible here.
The magma that cooled to form this rock originated in the mantle, undergoing chemical changes through interactions with the lower depths of the continental crust. Similar rocks also occur in the Adirondack Mountains of New York.