http://www.gemhut.com/agate.htm#agt325
and from the site:
http://www.helium.com/items/1101775-lake-superior-agates-treasure-hunting-agates-metal-detectors
How to find and identify agates
"...
Treasure Hunting for Lake Superior Agates. Did you know that the official gemstones of the state of Minnesota are called agates? Of all the beautiful rocks and gemstones that could have been considered, these beautiful stones that are readily available along so many beachfronts of that state are so treasured that they now have that official title. If you're interested in treasure hunting of any type, why not consider treasure hunting for some Lake Superior agates of your own?
These colorful rocks are more than just your garden variety types of stones. They were actually formed literally billions of years ago, when the North American continent began to split because of molten rocks shifting deep beneath the surface of the ground. Water vapor and carbon dioxide became trapped in areas of these lava flows, forming the colorful rocks we now call agates. Their beautiful and unique striped design is what makes them so treasured.
There are two ways to hunt for agates in the Lake Superior area. The first is to scuba dive in Lake Superior for these gemstones. A two hour non-certification class is offered in Copper Harbor and the class covers the location and identification of Lake Superior Agates. Air is furnished for this one tank dive class. Many of the better quality of agates are found on the sand bars in Lake Superior. The water is quite cold and can be very cloudy at times so always use the buddy system when diving.
The second way to hunt for agates is to search the lake shore of Lake Superior and nearby lakes. Hunting for Lake Superior agates isn't as easy as you might think. Their unique banding usually becomes more visible when the rocks are polished and cut a little bit, and not always visible to the naked eye. Prospectors often need to look for other clues when searching for agates. Most have a glossy or waxy appearance and a pitted texture. They also seem to have a glow or translucence on sunny days, usually because of the quartz deposit on the rocks. A brighter day is usually better for hunting than a cloudy one.
The best way to treat agates is by tumbling. This is when the rocks are put into a large vat with polishing grit and tumbled for several days until they are shiny and smooth. Usually areas where you can find Lake Superior agates have places that will do this for you, for a small fee. They may also have many specimens available that have been found by others and that you can purchase for your own. The larger ones are cut with diamond slabs until they're shiny and then are set in pieces of jewelry, belt buckles, and so on.
You don't need to be in Minnesota to find Lake Superior agates. Any waters that empty into Lake Superior will have deposits along the banks of their rivers and streams; up and down the Mississippi River is a great hunting ground for Lake Superior agates. Hikers, campers, and just casual beach goers have found a wealth of beautiful gemstones in many of these areas.
Treasure hunting takes on all forms these days; you can look for coins, shipwrecks, and even valuable rocks and gemstones. For a great vacation activity, why not try hunting for Lake Superior agates? They make great souvenirs for anyone..."
and from
http://www.helium.com/items/934631-how-to-find-and-identify-agates
"...
How to find and identify agates
by Karen Bledsoe
"Child finds precious stone in bucket of gravel!"
Maybe you've seen headlines like that and wished you could find gemstones yourself. There is one kind you can find easily, if you know where to look. Finding semi-precious agates may never make you rich, but agate-hunting can be a rewarding and colorful hobby.
WHAT AGATES ARE
Agates are transparent stones made up of quartz and a number of colored minerals. Silica - the same mineral that sand and computer chips are made of - dissolved in water creeps into small spaces in volcanic rock. When the silica is left behind it crystallizes. Slow crystallization results in large crystals that are valuable as gems: amethyst, rose quartz, and rock crystal are examples. Fast crystallization forms "massy," glass-like quartz such as agate, jasper, tiger-eye, aventurine, and onyx.
HOW TO FIND AGATES
Deposits of agate are usually found in igneous rock and are washed free by water erosion. Any place where rivers, streams, or the ocean wear away at volcanic rock you can often find agates: pebble-strewn beaches, gravel beds along rivers, rocky stream bottoms. Rocky shores where seashell hunting is a disappointment will often yield agates instead.
Patience is the key in agate hunting. Most hunters stroll slowly through patches of gravel, watching for a flash of color among the rocks. In strong sunlight, the clear agates will stand out against darker rocks. Hunting among wet pebbles is usually more productive, since wetness makes the colors brighter and the clear stones more obvious. On the beach, outgoing tides reveal freshly-churned gravel beds ready to be picked over.
Agate grounds along the west coast are often unpredictable, yielding a rich supply one year and none the next. Local rock shops will usually be happy to tell you where to look. For safety's sake, never turn your back on the sea. "Sneaker" waves can be extremely dangerous. Do not be tempted to climb cliffs and bluffs in search of agate veins. Climbing ocean cliffs is dangerous, environmentally unsound, and may involve trespassing.
TYPES OF AGATES
Carnelians are most common. They are transparent stones which may be rich orange-red, yellow, white, or brown, with little or no banding. The lightest forms are called Sard.
Moonstones are bright, milky white, clear stones. Moonstones with rainbows in them are called iris agates.
Ribbon agate has straight bands of color caused by different mineral impurities as the silica was deposited. If the bands are wavy, the stone is called fortification agate because the patterns often resemble medieval hill fortifications seen from above.
Picture agates are any kind of agate that have a mineral deposit that forms a figure. These are prized for jewelry.
Cloud agates, also called blue agates, are mottled with blue-black, blue, and milky colors. True blue agates are highly prized.
Moss agates don't really have moss in them. Mineral deposits form the branched, mossy patterns seen in these stones. Many form tree-like pictures, and are called landscape agates.
Jasper is another massy quartz stone found alongside agates. It is not transparent, but is often brilliantly colored. Jasper comes in red, yellow, and green.
Bloodstone is a type of dark green jasper with red spots. It is fairly rare. Bloodstone is sometimes called Heliotrope.
Petrified wood is formed when agate or jasper deposits replace wood. It is a type of fossil.
WHAT TO DO WITH AGATES
Because agate is a hard stone, it can be tumbled to a high polish. Inexpensive rock tumblers can be found at most hobby shops. It can take up to a month to polish rocks, so be patient. Hobby shops or craft shops may also sell jewelry "findings" (earring bases, key chains, etc.) to turn your tumbled stones into jewelry. Polished agates can also be piled into fancy jars for decoration, placed around cacti and small plants in dish gardens, or used in aquariums. Keep in mind that agates are a mineral deposit, so by no means are a renewable resource. Take only what you will use, and leave the rest for others to enjoy.
..."
and this from
http://www.dayooper.com/petoskey.htm
Michigan's Petoskey Stones
The primary mineral that makes up the fossil Colony Coral of a Petoskey Stone is Calcite. Petoskey Stones make excellent worry stones, paper weights and conversation pieces. Being Calcite, they are quite easily carved and the calcite will often allow the specimen to take a good polish and show the characteristics of the coral formation of the Michigan State Stone as shown in the background of this page.
The Petoskey Stone is a Six Sided Fossil Colony Coral (Hexagonaria percarinata) found along the beaches and in the fields and quarries of the Northern counties (Charlevoix, Emmet, Cheboygan, Presque Isle and Alpena Counties) of The Lower Peninsula of Michigan. Fossil hunters look for Petoskey Stones that have been weathered out of the Devonian reef limestone (Traverse Group) bedrock and dispursed by the Pleistocene glacerial and water action. The Michigan State Stone as normally found by rockhounds are smooth well worn pebbles and stones that have been rounded by glacerial and wave action. The fossil coral colony shows up in a pleasing turtle back pattern when wet or polished and rockhounding for Petoskey Stone is very popular.
And this from
Chlorastrolite (Green star light), a form of Pumpellyite, when polished, has a beautiful chatoyance (see greenstone on left) or play of light on the crystaline structures in the stone. Greenstones are relatively abundant, (except in gem quality) and can have salmon, pink, green, red, black and white inclusions and will occur rarely with inclusions of copper and/or silver.
Greenstones are found in the waters and on the shores of Isle Royale (hence the name) and in some areas of the Michigan Copper ranges of Lake Superior. Many of the old tailings of the mining era have Greenstones in them. Look for the dark green, small round or almond shape nodules in the poor rock. The problem of course is getting them out of the rock without damaging them. Sometimes they will have weathered out of the rock and can be found lying on the ground. You will find after all the hard work, that only a small percentage are greenstones, as most will be chloride, prehnite or some other mix of minerals. And of course, of all the greenstones found, perhaps 2 or 3 out of a hundred will be gem quality.
Greenstone specimen as a rule, are quite small. A pea-sized stone can be considered a nice specimen. Greenstone larger than this possessing a good pattern are extremely rare and hard to find.
You may order a Greenstone Specimen (Approximately 5mm) with a discription of Greenstone from Da Yooper for $10.00.
In the tourist shops of Copper Harbor, MI, the best jewelry quality greenstones are valued at up to $200.00 per carat and are in high demand by jewelers and collectors. Greenstone Jewelry is fast becoming popular, and the demand far exceeds the supply.
And from
http://www.dayooper.com/Greenstones.htm
Isle Royale Greenstone, ( Chlorastrolite ) a variety of Pumpellyite, Ca2(Al,Mg,Fe)3(SiO4)3(OH) * H2O, a Michigan mineral closely related to the epidote family, was named after Isle Royale, the island in Lake Superior on which they can be found. Good quality Greenstones are considered Semi-precious Gemstones of rare beauty. This Copper Country Mineral was officially named the Michigan State Gem in 1972 and the gem is slowly gaining in popularity outside it's area of renown. Principly because few gems can equal a high quality Isle Royale Greenstone for sheer beauty.
Chlorastrolite (Green star light), a form of Pumpellyite, when polished, has a beautiful chatoyance (see greenstone on left) or play of light on the crystaline structures in the stone. Greenstones are relatively abundant, (except in gem quality) and can have salmon, pink, green, red, black and white inclusions and will occur rarely with inclusions of copper and/or silver.
Greenstones are found in the waters and on the shores of Isle Royale (hence the name) and in some areas of the Michigan Copper ranges of Lake Superior. Many of the old tailings of the mining era have Greenstones in them. Look for the dark green, small round or almond shape nodules in the poor rock. The problem of course is getting them out of the rock without damaging them. Sometimes they will have weathered out of the rock and can be found lying on the ground. You will find after all the hard work, that only a small percentage are greenstones, as most will be chloride, prehnite or some other mix of minerals. And of course, of all the greenstones found, perhaps 2 or 3 out of a hundred will be gem quality.
Greenstone specimen as a rule, are quite small. A pea-sized stone can be considered a nice specimen. Greenstone larger than this possessing a good pattern are extremely rare and hard to find.
You may order a Greenstone Specimen (Approximately 5mm) with a discription of Greenstone from Da Yooper for $10.00.
In the tourist shops of Copper Harbor, MI, the best jewelry quality greenstones are valued at up to $200.00 per carat and are in high demand by jewelers and collectors. Greenstone Jewelry is fast becoming popular, and the demand far exceeds the supply.
