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History’s Gem of the Month

Fall 2009: Hints on Hunting and Finding Agates – PART II

Axel

While I was looking for something to include for this monthís history gem, I ran across yet another article written by Axel, which is different than the one that I included last month. This one is a rough draft, and required editing.

Hints on Hunting and Finding Agates
By Axel Niemi and Karen Brzys

There are two outward appearances to a Lake Superior agate. Some have the unworn outer look, while others have a worn or broken and chipped look. Most Lake Superior agates have an almond shape, called amygdaloidal. This denotes that the agate formed inside vacated gas pockets inside what was originally molten lava. As the gas gets trapped in the molten lava, the lava continues flowing, elongating the gas pocket. As the lava continues to cool, the pockets also harden, after which the steam escapes. Silicon dioxide quartz, with impurities of other minerals, later fills the pocket. The quartz and other impurities form submicroscopic crystals to fill in the pocket.

The unworn agate with original outer husk is more difficult to recognize. However, these unworn agates are usually only found where they formed, and must be mined out of the basaltic lava material. Most Lake Superior agates that have eroded out of the basalt are gravel-worn and easier to spot and recognize. All chipped agate has a waxy surface texture, which can expose the translucent nature of the microcrystalline quartz as well as the banded structure. Thus, in most cases when you are agate hunting on the beach, agates are rare but when you find them, it is usually obvious that they are agate. If you are not sure if it is an agate, it probably is not.

Several different types of agate can be found on the Lake Superior beach, some of which include:

  • Candy Stripe Agate: An agate with alternating red and white bands.
  • Carnelian Agate: A translucent agate with red to brown-red color. Carnelian can also form without banding.
  • Eye or Orbicular Agate: An agate with a circular eye formation on the outside of the specimen.
  • Fortification Agate: Agates with concentric bands.
  • Moss Agate: These agates have mossy looking mineral inclusions.
  • Paintstone or Dryhead Agate: These agates are not translucent due to the larger amount of impurities that are contained within the specimen. Many have pink and tan colors.
  • Peeler Agate: When agates are exposed to the weather, some of the bands may erode at a different rate than others. The result is an agate wherein the bands seem to have peeled back, like the layers of an onion.
  • Ruin Agate: These agates form with the pattern is broken, and then re-cemented back together by additional agate formation.
  • Sagenite Agate: These agates have many fine crystals, elongated and fan shaped, usually as an inclusion inside an agate. The fine crystal “needles” are usually formed by the mineral rutile.
  • Shadow Agate: These agates have tight banding with alternating opaque and translucent layers. As light enters the agate, it bounces between the layers. When you move the agate back and forth, you can see what appears to be a shadow, racing across the surface.
  • Tube Agate: In some cases, agate replaces other tube-shaped minerals forming interesting elongated patterns.
  • Water Level Agate: These agates have bands formed in parallel layers.

Remember that rockhounds never die, they just grind away.


History's Gems Archives

May 2007
(The Telescope Story)

June 2007
(The Story of the Grand Marais "Meteor")

July 2007
(Hints on Hunting Glacial Agate Article)

August 2007
(Lake Superior Origin from 1957)

Fall 2007
(Tourist Information from the 1920s)

December 2007
(Lake Superior Editorial)

January 2008
(Grand Marais Tourist Signpost)

February 2008
(Unusual Wedding Invitation)

March 2008
(1915 Rules for Teachers)

April 2008
(Cedar Stump article from 1962)

May 2008
(Old Postcards)

June 2008
(Pictured Rocks National Lakeshore Proposal Proposal Proposal-Part 1)

Summer 2008
(Pictured Rocks National Lakeshore Proposal Proposal-Part 2)

Summer 2008
(Pictured Rocks National Lakeshore Proposal Proposal-Part 3)

October 2008
(Pictured Rocks National Lakeshore Proposal Proposal-Part 4)

November 2008
(Pictured Rocks National Lakeshore Proposal-Part 5)

December 2008
(Agate Leaflet from 1927)

January 2009
(Old Postcards)

February 2009
(Snowstorm Article from 1988)

March 2009
(Lake Superior Agate Poem)

Spring 2009
(History of M77)

July 2009
(Axel Niemi Photo)

August 2009
(Ship Travel on Lake Superior)

September 2009
(Hints on Hunting and Finding Agates)

Fall 2009
(Hints on Hunting and Finding Agates Part 2)

February 2010
(The Story of Grand Marais Part 1)

February 2010
(The Story of Grand Marais Part 2)

April/May 2010
(The Story of Grand Marais Part 3)

June 2010
(Box of Rocks Gets Diploma)

July 2010
(Shipwrecks at Agate Beach)

August/September 2010
(1958 Detroit News Article about Axel Niemi)

Fall 2010
(Reprint from the Douglas Houghton Expedition)

Winter 2011
(Old Postcards and Pictures)

Spring 2011
(1905 Grand Marais Article)

September 2011
(Michigan Log Marks)

March 2012
(John Keating)

January 2012
(Axel Remembered)

March 2012
(John Keating)

June 2012
(The Shark: Post 1)

September 2012
(The Shark: Post 2)

March 2013
(The Shark: Post 3)

August 2013
(All That Glitters. . .)

November 2013
(Excerpts from The Grand Marais Herald)

April 2014
(Souvenir View Book of Sault Ste. Marie)

September 2014
(Michigan Beach Stones)

February 2015
(Michiganís Mystic Dunes)

June 2015
(Vintage Grand Marais Photos)

November 2015
(Gitchee Agomowin)

June 2016
(Grand Marais Poems)

August 2016
(1981 Article about Grand Marais)


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Grand Marais, Michigan 49839

 


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