Lake Superior Agates Questions

[roswelljero]

Lakers are mainly found in Canada, MN, WI & MI, right? Can they be found in other places south of there, like glacial morianes, rivers, etc?

Are Lakers translucent?

What makes an agate a Laker?


Later,
jeri

[frane]

Jeri, I really don't have the exact answers for you but I am going to comment just to bump this up. We have some great people that really know about them and maybe didn't see this post.
Fran

[Toad]

I don't see why they couldn't have been pushed south by glaciers, but then i don't know lakers. Probably has something to do with specific banding. Will wait with Fran for the experts to show. I'm curious too (and too lazy to search google right now)

[wyobrian]

not sure if these are laker's ? but they were found in Mississippi by my brother John (thunder69)


Brian

[superioragates]

Lake Superior agate
From Wikipedia, the free encyclopedia

The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone's geologic history in Minnesota. In 1969 the Lake Superior agate was designated by the Minnesota Legislature as the official state gemstone.

The Lake Superior agate was selected because the agate reflects many aspects of Minnesota. It was formed during lava eruptions that occurred in Minnesota about a billion years ago. The stone's predominant red color comes from iron, a major Minnesota industrial mineral found extensively throughout the Iron Range region. Finally, the Lake Superior agate can be found in many regions of Minnesota as it was distributed by glacial movement across Minnesota 10,000 to 15,000 years ago.

Geologic history
More than a billion years ago, the North American continent began to split apart along plate boundaries. Molten magma upwelled into iron-rich lava flows throughout the Midcontinent Rift System, including what is now the Minnesota Iron Range region. These flows are now exposed along the north and south shores of Lake Superior. The tectonic forces that attempted to pull the continent apart, and which left behind the lava flows, also created the Superior trough, a depressed region that became the basin of Lake Superior.

The lava flows formed the conditions for creation of Lake Superior agates. As the lava solidified, water vapor and carbon dioxide trapped within the solidified flows formed a vesicular texture (literally millions of small bubbles). Later, groundwater transported ferric iron, silica, and other dissolved minerals passed through the trapped gas vesicles. These quartz-rich groundwater solutions deposited concentric bands of fine-grained quartz called chalcedony, or embedded agates.

Over the next billion years, erosion exposed a number of the quartz-filled, banded vesicles -- agates -- were freed by running water and chemical disintegration of the lavas, since these vesicles were now harder than the lava rocks that contained them. The vast majority, however, remained lodged in the lava flows until the next major geologic event that changed them and Minnesota.

During the ensuing ice ages a lobe of glacial ice, the Superior lobe, moved into Minnesota through the agate-filled Superior trough. The glacier picked up surface agates and transported them south. Its crushing action and cycle of freezing and thawing at its base also freed many agates from within the lava flows and transported them, too. The advancing glacier acted like an enormous rock tumbler, abrading, fracturing, and rough-polishing the agates.

Description
The Lake Superior agate is noted for its rich red, orange, and yellow coloring. This color scheme is caused by the oxidation of iron. Iron leached from rocks provided the pigment that gives the gemstone its beautiful array of color. The concentration of iron and the amount of oxidation determine the color within or between an agate's bands.

The gemstone comes in various sizes. The gas pockets in which the agates formed were primarily small, about 1 cm in diameter. A few Lake Superior agates have been found that are 22 cm in diameter with a mass exceeding 10 kilograms. Very large agates are extremely rare.

The most common type of Lake Superior agate is the fortification agate with its eye-catching banding patterns. Each band, when traced around an exposed pattern or "face," connects with itself like the walls of a fort, hence the name fortification agate.

A common subtype of the fortification agate is the parallel-banded, onyx-fortification or water-level agate. Perfectly straight, parallel bands occur over all or part of these stones. The straight bands were produced by puddles of quartz-rich solutions that crystallized inside the gas pocket under very low fluid pressure. The parallel nature of the bands also indicates the agate's position inside the lava flow.

Probably the most popular Lake Superior agate is also one of the rarest. The highly treasured eye agate has perfectly round bands or "eyes" dotting the surface of the stone.

Occasionally, collectors find a gemstone with an almost perfectly smooth natural surface. These rare agates are believed to have spent a long time tumbling back and forth in the waves along some long-vanished, wave-battered rocky beach. They are called, appropriately enough, "water-washed" agates.
Cutting and polishing
A gemstone can be used as a jewel when cut and polished. Only a fraction of the Lake Superior agate are of the quality needed for lapidary. Three lapidary techniques are used on Lake Superior agates:

Tumbling—Small gemstones are rotated in drums with progressively finer polishing grit for several days until they are smooth and reflective.
Saw-cut and polish—Stones up to 1/2 kg are cut with diamond saws into thin slabs, which then are cut into various shapes. One side of the shaped slab is polished producing fine jewelry pieces and collectible gems called cabochons.
Face polishing—Polishing a curved surface on a portion of the stone and leaving the major portion in its natural state is called face polishing.
Distribution of Lake Superior agate
One of the most appealing reasons for naming the Lake Superior agate as the Minnesota state gemstone is its general availability. Glacial activity spread agates throughout northeastern and central Minnesota, extreme northwestern Wisconsin and Michigan's Upper Peninsula in the United States and the area around Thunder Bay in Northwestern Ontario, Canada.

Finding the gem
Typically the richly colored banding pattern is not well exposed and prospectors must look for other clues to the presence of agates.

The following characteristics are used to identify agates in the field.

Band planes along which the agate has broken are sometimes visible, giving the rock a peeled texture. It appears as though the bands were partially peeled off like a banana skin.
Iron-oxide staining is found on nearly all agates to some degree, and generally covers much of the rock. Such staining can be many different colors, but the most common are shades of rust-red and yellow.
Translucence is an optical feature produced by chalcedony quartz, the principal constituent of agates. The quartz allows light to penetrate, producing a glow. Sunny days are best for observing translucence.
A glossy, waxy appearance, especially on a chipped or broken surface, is another clue.
A pitted texture often covers the rock surface. The pits are the result of knobs or projections from an initial layer of softer mineral matter deposited on the wall of the cavity in which the agate formed. Later, when the quartz that formed the agate was deposited in the cavity, these projections left impressions on the exterior.

Maybe this will help
Marie

[roswelljero]

Thanks for your interest Fran & Toad.

Brian that 2nd one sure looks like the Lakers I've seen pics of.

Thanks for all the info Marie... So would you call the agates in Brian's pics Lakers?

Later,
jeri

[Toad]

Well, I guess that explains that. Thanks for posting the info, Marie.

[superioragates]

The 2nd one definetely looks laker, the first, maybe. I am no expert, so.......I do know I have found some with similiar coloring as that first one, but I have also found green with white banding, orange,white, clear, red, brown, blue, black and yellow. Northshorerocks showed me one he found that was purple, translucent, and I found a purple one with red banding, so it may be! There are so many diff. colors in lakers. I think it's the hardness (7.5-8 mohs) and location that specifically ID's the stones. My understanding of them is that they are the hardest, and oldest, but someone else may have something diff. to add to that. As far as can they be found further south.... I again am no expert, I only have the knowledge given to me by articles, and on this forum from members here.

[superioragates]

tube agate (laker)


These are a few I have found behind my house.

[Toad]

I haven't found anything anywhere near that interesting on Lake Erie.

[NorthShore-Rocks]

Lakers have been glaciated and pushed around several times. They have a fairly wide distribution. Bryan's pics look like Lakers. The second one is a "Candy-stripe Floater". The Mississippi produces some very nice rocks.

Here's a rough map showing the different lobes of glaciers and how far South they reached, overlapped and the driftless area. This map doesn't show the distribution of Lakers, but the middle lobe of the Wisconsin Glaciation period, dipping in to Iowa, is a key one.



Another thing that's important to remember in the distribution of Lakers, is the retreat of the glaciers. For a period of time, the retreating glaciers blocked the eastern travel of water through the Great Lakes and out the St. Lawrence. They acted as dams. All the natural occurring precipitation and melt water flowed down the Mississippi drainage.

Lake Superior was 500 to 1000 feet higher. You can still find that old lake shore here in Duluth. Skyline Parkway intersects that ancient beach in many places.

There must of been a tremendous amount of water flowing south. You can see evidence of this in many of the gravel pits in the area. 30 to 40 feet down from the surface, there's a thick layer that looks like the bottom of a stream. Flowing sand and various deposits of different size rock, all jumbled together and slightly tumbled!

[sdgoldpanner]

I have found some very nice Lakers around the North Platte River in Central & Eastern Nebraska. These too have had to come from that glacial movement.

[roswelljero]

WooHooo! It sounds like I could find one on the COR gravel bar! I'll have to pay more attention to the ugly, pitted rocks next time.

Thanks for the pics Marie. :drool: Can I come play in your backyard?!?!? "the hardness (7.5-8 mohs)" is that different from other agates?

Thanks for the map NorthShoreRocks. Gives me hope.

Later,
jeri

[aunuts]

Wow Marie, I love that tube agate. that's a beaut. you're a regular wealth of knowledge. once again, I'm impressed by the amazing depth of knowledge available on this forum.
jo

[superioragates]

I am not sure about "other agates" hardness. That would be a very good question for Mel (sabre52) or Steve (northshorerocks) to answer. This I do know for sure....Lakers are very tough to tumble in rotaries. They take forever!!! I have some that have been in rough grind all summer long, and they still haven't reached a place of moving on yet. I don't know about vibes, and if that would be faster or not, but these buggers are tough! Also...LOL...if yer gonna hunt'em, be prepared for neck and back aches like you wouldn't believe! For some reason they like to hide! That wikipedia article on lakers states they are "readily available", every time I read that, I have to snicker just a little cuz it just ain't so!!! My "back yard" by the way is a huge rock pit....maybe 200 feet or so behind my house, which I have spent hours and hours hunting in, and still have not covered it all yet. It stretches almost a mile....so...there are rocks I have not even seen yet waiting for me!!!!!!!!
Aunuts - that's the only "tube" agate I have been able to find....but it is awesome

[Toad]

You might get backaches - but the only rockpit near me is for limestone

[Hard Rock Cafe]

Well, they are readily available in that if you know where to look, you nearly always find one. One resource I read said that there is essentially an infinite supply of them. Finding them is the problem because most are buried. Most of what you'll find are chips off of much bigger rocks. The larger the rock, the lower the probability of finding one, especially one pound or more.

The photos in the OP definitely look like Lakers to me, especially the second one.

Steve's post is right on as to where they are found. They can be found all along the Mississippi as it transports material south.

Chuck

[agatemaggot]

The Glaciers (3 ) that came down thru Iowa pushed Agate all the way down to Missouri. The Glacial map is kind of misleading because there are Glacial deposits, ( some rather thin ) all the way down the river thru Iowa. The colors found in Lakers is amazing, we have found everything from White with clear banding to Black with White banding. We have several with Amy. crystal centers also. Finding one of those is usually the high-lite of the year !


Harley

[Toad]

Don't think Ohio made the map.