Author: Karen

The mineral of the month is my favorite agate: the shadow agate. This specimen was picked up off the Grand Marais beach by the museum founder, Axel Niemi. He found it in 1925 when he was just eight years old. He had it for almost 40 years when he finally sliced the agate, discovering the intricate banding. The best shadow agates in the world come from Lake Superior, Botswana Africa, and Queensland Australia.

Shadow agates exhibit an optical effect of movement across the bands. Depth is perceived from light penetrating and bouncing between alternating clear and opaque layers. When you move these agates back and forth, shadows can be seen racing across the surface. Many factors contribute to the shadow phenomenon including the regularity, contrast, distance, and depth of the bands. When the right conditions exist, light disappears into the clear chalcedony bands and is not reflected back out to the eye. When little or no light is returned to the line of sight, we interpret this as a dark region, or shadow.

It has been quite some time since I designated the Lake Superior Agate as the mineral of the month. In honor of the museum founder, I am featuring his 5.5 agate as the mineral of the month. He found this agate at the base of Grand Sable Dunes in 1958. He had it for many years before he gathered up the courage to cut a slice off the end. I am glad he made that decision, so that I didn’t have to. I have always wondered when he cut the agate. While preparing this month’s webpage update, I noticed for the first time the date in the article that appeared in the Oscoda County News article about Axel and his big agate. The article was published in October of 1979 and appears to showing the agate before it was cut. Since Axel left Grand Marais in around 1984 to be closer to medical facilities for his ailing wife, he must have cut the agate sometime between 1979 and 1984. If this is true, he had the agate for over 20 years before he cut off the end. If any of you remember anything more about when he cut the agate, please give me a call at 906-494-2590 or send me an email at karen @ agatelady.com.

The first photo shows the carnelian eye pocket that Axel spotted from what he claimed was 50 feet away. The next photo shows that whole side, which is the opposite side from where Axel took the slice off the end. The third photo shows the conchoidal fractures on the top of the specimen. Although you certainly can tell that it is agate, you would not have expected the banding quality that was exposed with the cut, shown in the fourth photo.

The last photo shows the agate face that resulted when Axel sliced off the end. Before it was cut, the agate weighed 5.5 pounds. Just for perspective, the cut face is 6” wide and 3” tall. The agate is also 4” deep. Over the last 10 years since opening the museum I have seen a lot of agates come off the beach. All in all, though, I still have not seen one that beats Axel’s 1958 wonder.

Amazonite, sometimes called Amazonstone, is a layered form of microcline feldspar; it was originally named after the Amazon River when similar green stones were found there. However, no deposits of Amazonite have ever been found near the Amazon River. Amazonite is a rare mineral. Originally, it was obtained from the Limen Mountains in Russia. More recently, it has been mined in the Pike’s Peak area of Colorado as well as in Madagascar, Canada, Italy, and Brazil.

Although Amazonite does exhibit a beautiful green color when polished, it is difficult to fashion into jewelry because it easily fractures. Most people believed that the blue-green color was due to copper compounds. Scientists discovered in the mid-1980s, though, that the color is caused by small quantities of lead and water.

Amazonite is a relatively soft stone, ranging from 5-6 on the Mohs scale. It has a specific gravity of around 2.56. It has a vitreous luster and can be translucent, or opaque if it contains a greater amount of impurities. It has a conchoidal fracture, but an also split between the layers. Because of the crystal structure within the mineral, it produces the schiller effect similar, but not quite as dramatic, as Labradorite.

It is thought that amazonite is a soothing stone that can improve self-confidence. It can also inspire confidence and positive attitude, and therefore can also diminish fear and anxiety.