Gitche Gumee Agate and History Museum

Navigation Menu


Photo Gallery - Mineral of the Month

Click to enter our class!
Leave a message



August 2016 - Puddingstone

In central Ontario and eastern Upper Peninsula of Michigan, in the area around northern Lake Huron, rockhounds can find puddingstones. These jasper conglomerates formed during the Huronian Period of the Proterozoic Era around a billion years ago. Erosional forces were dramatic at the time since vegetation had not yet evolved, so exposed rock quickly wore down. Sediments from this erosion were deposited on the bottoms of large bodies of water including sand as well as red jasper pebbles and other small stones. Over time the weight of the piled sediments caused the components to cement together forming large masses of conglomerate rock. The conglomerate masses subsequently eroded and broke apart. Some of the loose fragments and puddingstones were distributed around the area by the Labrador ice sheet.

The Puddingstone was named by British settlers who lived along the St. Mary’s River and Northern Lake Huron. They believed it looked like Christmas pudding. Puddingstones range in size from a small pebble to boulders larger than trucks!

Puddingstone conglomerate rocks are made up of a mixture of different, irregular sized grains and pebbles held together by a finer matrix, usually formed from quartz sand. The sedimentary rock is formed in river channels and may contain various minerals such as chromite, corundum, platinum, diamond, gold, sapphire, and zircon. The rounded imbedded pebbles have a sharp contrast in color to the rock’s matrix. In addition to the puddingstone rocks found in Michigan and Ontario, there are different types of puddingstone, with different composition, origin, and geographical distribution found in:

Hertfordshire puddingstone, principally found in Hertfordshire, England Bearfort Mountain puddingstone, is a purple puddingstone found in northern New Jersey.

Roxbury puddingstone, principally found in and around Boston, Massachusetts.

Plumstead Common, located southeast of London, England, has a fine example of puddingstone, probably left behind after the last Ice Age.

CITES puddingstone.html


James G. Kelley,

Mineral of the Month Archives

May 2007: Rainbow Fluorite

June 2007: Lake Superior Michipicoten Agate

July 2007: Labadorite

August 2007: Rain Flower Agate

Fall 2007: Malachite

December 2007: Nepheline Syenite

January 2008: Native Copper

February 2008: Amazonite

June 2012: Moqui Marbles

March 2008: Lake Superior Agate

April 2008: Shadow Agate

May 2008: Apohpylite

June 2008: Ocean Jasper

Summer 2008: Marra Mamba Tiger's Eye

September 2008: Mohawkite

October 2008: Mexican opal

November 2008: Prehnite

December 2008: Picture Jasper

January 2009: Sea Shell Jasper

February 2009: Polychrome Jasper

March 2009: Selenite Desert Rose

Spring 2009: Coyamito Agate

July 2009: Obsidian Needles

August 2009: Goethite

September 2009: Banded Iron Formation

Fall 2009: Fairburn Agate

March 2010: Fossilized Dinosaur Bone

April/May: 2010 Kentucky Agate

June 2010: Nantan Meteorite

July 2010: Mookaite Jasper

Aug/Sept 2010: Polyhedroid Agate

Fall 2010: Ammonite Fossil

Winter 2011: Argentina Condor Agate

Spring 2011: Petrfied Wood

September 2011: Petoskey Stones

January 2012: Mary Ellen Jasper

March 2012: Mexican Crazy Lace Agate

September 2012: Chlorastrolite Greenstone

March 2013: Jacobsville Sandstone

August 2013: Unakite

November 2013: Skip-an-Atom Agate

April 2014: Tiger's Eye

September 2014: Black Corundum

February 2015: Condor Agate

June 2015: Petoskey Stone

November 2015: Slag

June 2016: Lake Superior Copper Replacement Agates


Copyright All rights reserved.
Gitche Gumee Museum.
E21739 Brazel Street
Grand Marais, Michigan 49839


Web Site Designed By
Web Site Design ServiceSearch Engine Optimization Firm