Lake Huron Puddingstones

Puddingstone, also known as Jasper Conglomerate, Pudding Stone, Lorrain Conglomerate, Quartz Conglomerate, Plum Puddingstone is a rare conglomerate found in only a few places in the world. Puddingstone was named by Cornish miners who thought the stone resembled their traditional Christmas pudding made with raisins, cherries, currents and nuts.
In Michigan, in Lake Huron, St. Joseph and Drummond Islands produce a distinct Puddingstone. This stone forms in a semi-transparent quartzite, sandstone matrix. The matrix, background, main rock is usually white, cream, sandy but can be a wide variety of colors with pinks, greys and browns included.
The inclusions, pieces of imbedded pebbles & stones, can vary as well. Jasper, from bright, lipstick red to browns, purples, oranges and pinks, is the main inclusion. Other minerals could be quartz, chert, hematite, black flint, green quartz, and even fossils.
This journal is my research into the wonders of Lake Huron Puddingstone.

Tuesday, July 29, 2014

What is Pudding Stone? A definition

Here is the definition of "Pudding Stone" from the book "Michigan Rocks & Minerals" by Dan R. Lynch & Bob Lynch:
 "Pudding Stone, like Michigan's granite, is another case of "foreign" rocks making their way south via the glaciers of past ice ages. Pudding Stone formed in Canada and is a type of conglomerate rock that has undergone metamorphosis; it has been greatly compacted and hardened due to pressure.
  It originally consisted primarily of gravel-sized pieces of jasper, chert and quartz, though after such intense hardening and cementing together, the quartz has actually become a variety of quartzite. The jasper and chert pieces are randomly sized and shaped and are generally quite limited in relation to the amount of quartzite.
 This metamorphosed conglomerate derives it's curious name from its appearance. Long ago, discoverers thought that the bright red jasper fragments resembled fruit and the dark chery looked like nuts, with the white quartzite being the "pudding" they floated in.
  It is this characteristic appearance that should be enough to identify it."

I really like this definition! It's straightforward and easy-to-understand. I'd recommend it for Michigan rock hounds.
 I think the definition helps me to eliminate some stones that I was erroneously calling Puddings. Such as this one;

I believe this to be a Conglomeration due to it's very prolific inclusions, no clear quartzite matrix and little actual jasper.

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