In 1890 an author named Saxe Holm wrote a charming story entitled, My Tourmaline. The young heroine possesses a crystal of tourmaline, which she finds in the roots of a large tree. It brings her good fortune until she loses it. Bereft until she finally finds it in someone else’s collection, she and her tourmaline are eventually re-united and live “happily ever after.”
What is it about tourmaline that makes people feel so connected to it? One reason is because of all the colors it comes in. There is no other mineral that comes in as many hues. This rainbow quality translates to a lightness and happiness that appeals to all. It also suggests tolerance, flexibility and a compassionate understanding. The Sri Lankans named the gem, “turamali”, meaning a stone of mixed colors.
A rainbow of gemstones, all of them are tourmaline.
Another quality of tourmaline is its pyroelectricity. If heated, it actually has magnetic properties. As a result, the mineral has many industrial uses. You can find it in hairdryers to calm static hair, in joint wraps to promote blood circulation, and in tuning circuits for conducting TV and radio frequencies. In the metaphysical world, tourmaline is seen as a strong protector, reflecting negativity away from anyone possessing the stone. It’s also seen as a grounding stone that promotes a sense of power and self-confidence.
Finally, tourmaline is a popular gemstone, featured prominently as the birthstone for October and the anniversary stone for the 8th and 38th anniversaries. It has a hardness of 7 – 7.5 on the Mohs scale, so it’s durable enough to be set in rings. It’s not as expensive as ruby, emerald, or sapphire, but it can sometimes mimic these colors. And it’s mined on almost every continent– from the state of Maine to the island of Madagascar.
You may own a tourmaline and not even know it, because the gem has so many trade names. If you own a rubellite, an indicolite, a verdelite, a siberite, an achroite, or a paraiba, you actually own a tourmaline. You may also have a bi-colored or parti-colored tourmaline, a watermelon tourmaline, or even tourmalinated quartz! There are so many different looks to this versatile mineral. If these pictures are motivating you to own a tourmaline (or a second one), stop in our store. We’d be happy to introduce you to the ones in our showcase.
Watermelon tourmaline earrings with rubellite and green tourmaline: custom-made by our benchjewelers
Tourmalinated Quartz: The black crystals are the tourmaline, also called schorl.
Watermelon tourmaline, carved into butterfly wings, and made into a pendant by our benchjewelers
There are four green sand beaches on Earth. One of them, Papakolea Beach, is at the southern tip of the Big Island of Hawaii. And I was lucky enough to go there this January, during my 2-week vacation in the Hawaiian Islands. (Side note: If you ever get the chance to go to Hawaii, TAKE IT!) This beach isn’t easy to get to, as it’s about two and a half miles from the dirt parking lot. Your choices are a “shuttle” which is actually an old van or pick-up truck for $15, or a good 45 minute walk. Both choices leave you dusty and thirsty, as you make your way towards an amazing oasis.
The Green Sand Beach
Why is the sand GREEN? Well, the answer lies under the crust of the Earth, in the upper mantle, where one of the dominant rocks is Peridotite. The name may remind you of August’s birthstone, Peridot, whose color is a yellowish to brownish green. Peridotite is brought to the surface on the waves of magma that erupt from the same volcanos that formed the Hawaiian Islands. It’s made primarily of the mineral, Olivine, which has a much higher melting temperature than most minerals. So, the magma brings it to the surface, surrounds it with lava rock (basalt), but doesn’t melt it into the mixture. These peridotite xenoliths eventually reveal themselves as erosion breaks down the basalt host rock.
What happens next is what happens to every rock, given time and exposure to the elements. The peridotite breaks into smaller and smaller pieces, until it’s a bunch of tiny olivine grains. But these little grains are heavier than most sand, so if the conditions are protected enough, they have a tendency to stay. And if enough of them stay in one place, it makes the beach look green. Conditions are rarely as perfect as here in this bay, cut by the ocean into the side of a former cinder cone.
So, how does it feel to play on a beach of green gems? The truth is, most peridotite is not gem quality, and grains of sand are way too small to be valuable. But there is something special, at least to this gemologist, about having tiny peridot between your toes. It was great building a sand castle out of what the Hawaiians call their Hawaiian Diamonds.
The sand is protected by the state, so you’re not allowed to fill a container with it unless you are a native Hawaiian. But, wouldn’t you know, the driver of my shuttle was a twelfth generation Hawaiian, and he was trying to impress the young, pretty woman sitting next to him. He gave her a handful of green sand, mixed with larger peridot pebbles, in an empty water bottle. When she showed them to me, I gasped in delight. “Oh, my gosh!” I exclaimed. “They’re beautiful!!”
When she found out I worked with gemstones, she secretly gave me the water bottle, saying, “You’ll appreciate it so much more than I will.” So, I have my special little stash of green sand which I will keep forever!
Hawaiian Diamonds (aka The Tears of Pele–Goddess of Volcanos)
Jewelry is made of things from the earth–like metals and minerals. Or it’s made of animals from the sea–like pearls and coral. But meteorite is one material used in jewelry that doesn’t come from the earth or the sea. Meteorite is extraterrestrial material, recovered after it hits Earth. It’s used a lot in men’s wedding bands, and its use is starting to seep into women’s pendants and bracelets.
Lashbrook’s Meteorite Men’s Wedding Band
What is meteorite made of? Well, it depends on which type you’re thinking about. The three types are stony, iron, and stony-iron. Only 5% of meteorites are classified as iron, but they are the ones that are used for jewelry. These meteorites are primarily iron but contain trace elements like nickel, cobalt and gold. The metal shows a distinctive crystalline pattern when cut, polished, and acid etched. The pattern is the result of slow-cooling iron and nickel crystals.
One manufacturer of men’s wedding bands, Lashbrook, uses material from the Gibeon meteorite. The Gibeon material is found near the town of Gibeon in Namibia. Turns out that all meteorites are named for their location. It’s believed the tons of material that showered Gibeon 30,000 years ago is about 4 billion years old.
Suppose you want a piece of outer space in your ring. After all, how cool is that? But you should know a few things first. Iron meteorites are magnetic so, if your job is working with magnets, you may want to reconsider. If you have a nickel allergy, you shouldn’t wear meteorite. Gibeon material is about 9% nickel. And, even if none of the above holds true for you, you will want to treat your ring with care. It’s important to never wear it in a pool or hot tub. Because iron can rust, keep the ring dry as much as possible. If you do notice rust, rid the meteorite of any moisture by soaking it in 90% rubbing alcohol and then air drying it. You can clean it gently with a soft toothbrush, and then apply a small amount of gun metal oil, wiping away any excess. Finally, the etch pattern that makes meteorite so distinctive can wear down and become fainter over time. It is possible to re-etch the pattern, however.
A raw piece of Seymchan Meteorite
One thing that surprised me was how many meteorites exist on Earth. Over 40,000 have been found and cataloged. Small pieces of meteorite fall to Earth everyday, but most of them are small and impossible to find because they fall into an ocean! If you want to look for iron meteorite, here are a few tips. Look in regions that are dry and have a barren expanse, like the Mohave Desert or the Great Plains. The black to dark brown color of a meteorite’s exterior, due to the fact that it’s on fire when it enters our atmosphere, is easier to see when the land is tan-colored and without vegetation. Also, the dryness of desert areas helps keep the meteorite from rusting. Use a metal detector to find iron meteorites. And check with the land owner before beginning your search. It’s usually okay to search on public land, but you can’t take any specimens from a National Park.
I have only one tip if you want a meteorite ring. Come to Dearborn Jewelers!!
I’ll never forget vacationing in Thailand, trying to decide whether to buy a pair of jadeite earrings. The beaming salesman chanted to me, “Burmeeeese jade,” with a knowing nod. His smile implied that nothing could be better.
Imperial-quality jade. Courtesy of Mason-Kay.
That was about eight years ago, when jade and rubies from Burma (Myanmar) were banned from the United States. Retailers in the U.S. could not sell them. Wholesalers could not import them. Well, that recently changed, and the announcement got me interested in the story of how these gems came to be sanctioned.
It was back in 2003 when George W. Bush signed the trade embargo, prohibiting the import of Burmese goods. The military ruling group, the “junta”, of the country had imprisoned the people’s leader, Aung San Suu Kyi. Citizens of the country were having their human rights violated. The embargo was a response to what was considered an unacceptable way to govern.
But there were loopholes in the 2003 document, and Burmese jade and rubies still found their way into the U.S. If a “middleman” country got involved, either in the cutting or polishing step, it was still legal to import these gems to the U.S. That is, until July 2008.
President Bush signed a new document, the Tom Lantos Block Burmese J.A.D.E.(Junta’s Anti-Democratic Efforts) Act, which closed the loopholes and effectively banned the import of ALL precious Burmese gemstones. Wholesalers and retailers selling ruby and jade needed documentation to certify that the gems had not originated in Burma.
The jewelry industry was negatively impacted by the embargo. Burma was considered the best source in the world for fine ruby and jade. Different sources of the gems had to be found, and, over the years, they were. Today many rubies come from Mozambique. Jadeite sources include Guatemala, Japan, and Kazakhstan.
The trade sanctions had the desired effect. Myanmar began to make reforms in 2010. Over the next couple of years, democratic elections were held and many political prisoners were released. In 2011, the U.S. appointed an ambassador, and, in 2012, President Obama visited the country. Using a cautious approach, President Obama lifted some of the sanctions in November 2012. But the ban on rubies and jade remained in place.
Aung San Suu Kyi, who is now the nation’s State Counsellor (sort of like a Prime Minister), expressed patience, saying that “We believe that if we are going along the right path, all sanctions should be lifted in good time.” And she was right! On October 7th, 2016, President Obama signed an executive order to lift the remaining trade sanctions against Myanmar.
It will be interesting to see how this executive order influences the jewelry industry in the coming months and years. It will take some time to establish or re-establish relationships with Burmese stone dealers. But I believe it won’t be long before we see the deep blood-red Burmese rubies back in our stores. And my “Burmeeeese” jade earrings (Yes. . . I bought them) may soon be easy to find in the United States.
25.59 carat Burmese Ruby, sold in 2015 for $30.3 million
A large polished piece of Greenstone
In late September I was in Swede’s, the famous light blue jewelry and rock store in the middle of Copper Harbor, Michigan. The feisty woman in charge, 83-year-old Mary Billings, asked me as I walked in–“What is the gemstone of Michigan?”
When I answered, “Isle Royale Greenstone,” she looked at me with new respect.
“You’re only the thirteenth customer this season who has answered that question correctly. And we’ve had a lot of people who’ve walked through that door.” She shook her head, a little disgusted that Michiganders weren’t commonly aware of their state gemstone.
Most people, if they have any idea at all, would probably say Petoskey is the state’s gem. And it IS the state rock. But Isle Royale Greenstone, or just Greenstone, has been Michigan’s official gem since 1973. Found mainly on Isle Royale or the Keweenaw Peninsula, Greenstone has the fancy, scientific name of Chlorastrolite, which is a variety of the mineral Pumpellyite. It’s often found in and around copper mines, which are abundant in the Keweenaw. The mineral makes its home in amygdaloidal basalt. If you’re like me, that phrase holds no meaning. I had to look it up, so I’m happy to share its meaning. Basically it’s a pit or cavity in the stone. So amygdaloidal basalt is cooled and hardened lava with lots of cavities in it that have been filled in with minerals.
Once the Greenstone is removed from its host rock, it can be cut and polished. But it’s a tricky stone to work with because it’s not really hard–only a 5-6 on the Mohs’ Scale– and it can have its own cavities and hollow spots within it. Cutters want to expose the best “turtle-back” pattern that they can and eliminate any bad spots. But removing a top layer of the stone is likely to reveal a different, and not necessarily better pattern. The goal is a clear pattern showing some chatoyancy. The best stones will demonstrate that change in luster as they are tilted back and forth in the light.
Tumbled Greenstone with pink Thomsonite
Greenstone is not a particularly expensive gemstone to buy. Even with the labor involved in finding, mining, and cutting it, there’s just not a huge market for the material. But it isn’t an easy gem to own. Since the year 2000, it’s been illegal to take Isle Royale Greenstone off the island. The island is, after all, a national park. And even Keweenaw Greenstone isn’t easy to get unless you have access to the copper mine areas. Most jewelry stores, even in Michigan, don’t carry Greenstone. So plan on spending some time searching for your perfect piece of Michigan’s gemstone. Whether you spend time looking along the shoreline for a rare small piece of it, or whether you search for jewelry stores that carry the gem, enjoy the journey.
My piece of Keweenaw Greenstone! I love it!!
Have you ever heard of Crater of Diamonds State Park in Arkansas? The place where you can sift through the dirt and look for the sparkle of a diamond? I so wish my parents had taken me here when I was a kid!! Even though the possibility of finding a diamond is small–only about 1-2% of all visitors leave with one–the probability of having a good time is very high.
Crater of Diamonds has been a state park since the early 1970s. The park encompasses over 900 acres, but 37 of those acres sit on a volcanic pipe. This pipe, which was part of a 95 million year old volcano (long since eroded), carried diamonds to the Earth’s surface. Today, Crater of Diamonds is the only diamond-bearing site that is open to the public. For eight dollars you can search from morning til night. The park has exhibits and videos that give you the history of the area as well as good tips on how to search for diamonds. It has equipment you can rent, things like shovels and sifting screens, or you can bring your own. Over the years the park has been the location for some remarkable stories.
The biggest diamond ever found there, or anywhere in the U.S., was a 40.23 carat stone called Uncle Sam. It was found back in 1924, when the area was still owned by a diamond mine. Other big finds have been made over the years. As recently as 2015, an 8.52 carat diamond was found, and has been named Esperanza. Most of the diamonds found, however, are small. Approximately 90% of the diamonds are less than 1/4 carat, which is only about the size of a match head . The diamonds from this site are yellow, brown, or colorless. They are not easy to find, but one feature that helps is that they look polished, almost as if they have an oily film on them. Also, they’re usually translucent, which means you can see into them but you can’t see through them. If you’re not sure what you’ve found, there is an expert at the site, ready to help you with identification.
The park is a popular place. It had 168,000 visitors last year. In addition to looking for diamonds, there is a water park and camping. It sounds like the place for a perfect day, if you’re a kid. Go get dusty and dirty looking for rocks, and then get cooled and cleaned off at the water park! Heck, it sounds great even if you’re not a kid!!
If you’d rather look for colored gems, amethysts, garnets, and agates have also been found at Crater of Diamonds. But there are, perhaps, better locations in the U.S. if you’re rockhounding for colored gemstones. Check out Gem Mountain in Montana for sapphires. Or Emerald Hollow Mine in North Carolina for emeralds, rubies, and aquamarine. Morefield Mine in Virginia is a source for amazonite, beryl, garnet, amethyst, and topaz.
It’s not too early to start planning next summer’s vacation. Ask your kids and they’ll tell you–“We want to dig for gemstones!”
Flawless Quartz Crystal Sphere at the Smithsonian Natural History Museum (106.75 lbs)
This crystal sphere is the largest cut piece of flawless quartz in the world, weighing in at 242,323 carats! It symbolizes our fascination with something so beautiful and yet so common. Quartz is found around the world, in large quantities, and is considered one of the most common minerals on Earth. It’s found in sand, dirt, and dust. Yet, when fashioned by gem cutters and put in a stunning piece of jewelry, it can be breathtaking.
Quartz is a complicated gemstone. One of the reasons it’s tricky is because the term “quartz” is used for varieties of gems, as well as for a species of gem and as a group of gems. So, for example, Rose Quartz is a variety of the species Quartz. So is Citrine, Amethyst, and Tiger’s Eye! All these varieties, and others that are couched under the species of Chalcedony, such as Agate and Jasper, are considered to be members of the group, Quartz. Very confusing!!
Perhaps it’s best to start with the fact that mineralogists and geologists see any mineral with the chemical makeup of silicon dioxide, SiO2, as Quartz. Regardless of whether the crystals making up that stone are large, small, or microscopic, it’s all Quartz. Gemologists, on the other hand, separate the gems into those whose crystals are larger and those too small to see without a high-powered microscope. Those with larger crystals are called Quartz and those with microcrystalline structures are labeled Chalcedony.
Under these two species are many varieties that are used in jewelry. Probably the most commonly known variety of the quartz species is Amethyst. That regal purple has been admired for centuries. The purple color comes from natural irradiation acting upon a trace element of iron. The saturated, medium to deep reddish purple is the most prized color, but amethyst ranges from a light, pinkish purple to that deep purple hue. Amethyst is not rare, but the prized color is more rare because usually only the tips of the amethyst crystals have that depth of color.
Agate and Amethyst, showing the deep purple tips of the quartz crystals, as well as the microcrystalline Agate, which is part of the Chalcedony species.
Other varieties of the Quartz species include Citrine, the orange-yellow gemstone that’s November’s birthstone, and Rock Crystal, which is colorless because it has no trace elements. There’s also Rose Quartz, Smoky Quartz, Prasiolite (aka Green Amethyst), and Ametrine (a bi-colored gem combining the purple of Amethyst and the yellow of Citrine).
Members the Chalcedony species have been used in jewelry even longer than Amethyst! Agates, which exhibit wavy bands of color, were used in amulets and talismans over 3000 years ago. They were also used to make cameos. Carvers would reveal a differently colored band by carving down around the subject of the piece. Today you’ll see agate slice pendants that are sometimes dyed to accentuate the banding.
Probably the most valuable member of the Chalcedony species is Chrysoprase. This translucent gemstone is beloved for its natural apple-green color. It owes its color to the presence of nickel. A big discovery of Chrysoprase was made in 1965 in Australia. Because its color can resemble fine jadeite, it’s sometimes called “Australian Jade.”
Other varieties of the Chalcedony species include Black Onyx (dyed black chalcedony), Carnelian, Jasper, and Fire Agate. Most chalcedony is translucent to opaque, so it’s rarely faceted. Most often it’s fashioned into beads, slices or cabochons. But, just like all Quartz, it registers a 7 on the Mohs Hardness Scale, making it a good choice for rings and bracelets as well as earrings and pendants.
There’s so much that can be said about this beautiful mineral that surrounds us everyday. But I want to end with the sentiment– “How wonderful when something so common can also be so special!”
Custom-made Ametrine Ring in our showcase!
The romance and history of colored gemstones has always fascinated me. I guess I’m just a sucker for a good story. Here are three I thought you might like.
TANZANITE: It’s said that we are all members of the “Tanzanite generation.” Discovered in 1967 by a Masai tribesman in Northern Tanzania, Tanzanite is mined in only one, 4 square kilometer, location. And the mines are getting deeper and harder to mine profitably. We will be the ones who can buy a new Tanzanite. Future generations will only see the stone in heirloom pieces. It’s estimated that Tanzanite One, the largest Tanzanite mining company, has less than 30 years of production left.
The gemstone was named by Henry Platt, great-grandson of the famous Louis C. Tiffany. Tiffany and Co. realized the importance of the gemstone and quickly made themselves the main distributor. Their marketing efforts made tanzanite one of the most popular gemstones by the 1990s. The beautiful gem hit the big screen with a “splash” as the Heart of the Ocean in the movie, Titanic.
MORGANITE: This pink to orange/pink variety of beryl was originally discovered in Pala, California in the early 1900s. It was named for J.P. Morgan, a great financier and collector of minerals. Tiffany’s gem buyer and gemologist, George Kunz, was the man who named the gem, buying up all he could find for his wealthy client. Incidentally, another pink gemstone, discovered at about the same time, was named Kunzite in honor of George Kunz. So, he got his own gemstone, too!
Morganite is the same species of mineral as Emerald and Aquamarine. Like Aquamarine, it is usually an eye-clean stone that can be cut in larger sizes. It’s a good thing, too, because a larger stone usually shows a more saturated color. Pale Morganite often needs that advantage. It’s generally heat-treated to improve its pink color and minimize its yellowish tint. The treatment is stable, so no fading occurs.
ALEXANDRITE: First discovered in Russia’s Ural Mountains in the early 1830s, Alexandrite is the quintessential color-change gemstone. It was found by miners who thought they’d found emeralds, until nighttime came and they were sitting around the campfire. Alexandrite’s trace elements of iron, titanium, and chromium make it greenish in sunlight and reddish in incandescent or fire light. Boy, were those miners surprised when, the next morning, their red gemstones had turned back to green!
Legend says that the gem was found on the 16th birthday of young Alexander II, future Czar of Russia. The stone became the National Gem of Czarist Russia. It was the perfect fit with the red and green color scheme of imperial Russia’s military. Every Russian had to have an Alexandrite. Unfortunately, for all of us, the Russian supply was depleted. Fortunately, other deposits have been found in Sri Lanka, East Africa, and Brazil.
Natural Alexandrites are very expensive, especially in larger sizes. Even the synthetic version is expensive, because it’s difficult to manufacture. But, if you’re lucky enough to own an Alexandrite, you have an “Emerald by day, and a Ruby by night.”
I’ve lived most of my life in Michigan and my maiden name is Campbell. Most people don’t know that because I’ve been married so long! But I always thought Campbell was a good name, so I was both happy and surprised to learn that there is a gemstone named after. . .no, not me, nor my kinfolk, but after the Campbell shaft of the well known Bisbee Mine in Southern Arizona.
So, what’s the story of Campbellite? As explained by one of the stone cutters at Arizona Lapidary, Campbellite is an uncertain mixture of minerals like cuprite, azurite, malachite, calcite,chrysocolla, pyrite, quartz, and copper. Its color and look varies because there’s no set amount of these minerals. It was first discovered by miners looking for copper. The bosses weren’t interested in this unusual rock, and told the miners to discard it. But the miners had a different plan. They saw its beauty. So, yes, they dumped the Campbellite in the trashcan. But they separated it carefully from the real trash. And when no one was looking, they loaded the discarded gem into the back ends of pickups. Campbellite has been showing up in the market, piece by piece. There’s not a lot of it–I’m sure plenty WAS dumped. The mine closed in 1975, and there is no other known source of Campbellite. But I bought one piece of it, cut into a smooth cabochon, and plan to make a bolo tie for my dad.
I learned a little bit about the mine shaft itself. It was first developed in 1927, originally as a way to get oxygen to other parts of the Bisbee Mine. But soon it was one of the best producers of copper ore, with yields of 8-10% copper.
Finally, who is the Campbell shaft named after? A little research revealed an amazing coincidence. The shaft was named after Gordon R. Campbell, who actually lived and went to school in Michigan! He graduated from U of M in 1893 and was a mining executive and lawyer up in the Keweenaw Peninsula. The Keweenaw Peninsula, jutting from the Upper Peninsula of Michigan, is one of the best known sources of copper world-wide. Towns like Calumet, Houghton, and Copper Harbor were booming back in the mid-1800s because of copper. Anyway, Gordon Campbell helped form the Calumet and Arizona Mining Company in 1901, serving as the company’s President from 1921-1931. It was this company that operated the Bisbee Mine. So Campbellite WAS named for a Campbell living in Michigan. Who knows? Maybe he’s a long, lost cousin?
The Campbell shaft, courtesy of the Arizona Historical Society
Lake Superior Agates
If you’re a Michigander like me, you grew up going to one of the Great Lakes for a day at the beach. As a kid, I didn’t know how lucky I was to witness the variety of minerals and rocks along the lakeshore. No where else in the world can you see that variety. I would look for our state rock, the Petoskey stone. I didn’t even know that Michigan had a state gem, the Isle Royale Greenstone (aka Chlorastrolite.)
I’ve always been a rock hound of sorts, and many Michiganders share my passion. There’s so much to know about our rocks and minerals. Most of the information in this post comes from a great book called, Michigan Rocks and Minerals, by Dan and Bob Lynch. I’d highly recommend it if you’re a serious rock hound.
Their book brought up questions I’d never considered before.
*What’s the difference between a MINERAL and a ROCK?
A mineral is a crystallized version of a chemical compound. Most gemstones are minerals. For example, a diamond is crystallized carbon. Quartz is crystallized silicon dioxide. Rocks are a conglomerate of minerals. Lapis Lazuli is an example of a gem that’s actually a rock. Its main ingredient is lazurite, but it also has minerals like calcite, pyrite, and mica. While minerals have characteristics, such as hardness or refractive index, that can be identified throughout the mineral, the characteristics of a rock vary depending on which spot of the rock you’re testing.
*What’s the difference between rock hunting in the Upper Peninsula vs. the Lower Peninsula?
The U.P. and L.P. are geologically very different. The U.P. is formed from volcanic rock. It is rich in the elements of copper, iron, manganese, and even gold. Those elements lend themselves to minerals like azurite, chrysocolla, and hematite. The L.P. is formed from sedimentary rock. It has a lot of limestone, shale, and gypsum. Most of the pretty Michigan minerals, in my opinion, are found in the Upper Peninsula.
*What are some basic tools needed to identify rocks and minerals?
If you do want to do some rock identification, you’ll need a few simple tools. Of course, an identification book is necessary. But one of the main ways to identify a rock is by its hardness. The Mohs Hardness Scale measures minerals from 1 to 10, with one being the softest and ten the hardest. Most minerals in Michigan fall between 2 and 7. You can estimate a mineral’s hardness using a scratch test, taking care to scratch the specimen in an inconspicuous place. Your fingernail will scratch a mineral of 2.5 hardness or less. A copper penny will scratch a mineral of 3.5 hardness or less. A piece of glass or a steel knife works on minerals of 5.5 or less, and a piece of unglazed porcelain works on minerals of 6.5 or less. So these four inexpensive tools can really help you narrow down the options when you want to identify your find.
Michigan Rocks and Minerals discusses over 200 different materials, giving details such as hardness, common size, and color. The book has color photos of the materials and gives suggestions of where to look for them. I’ve decided I want to look for Lake Superior Agates, Dolomite, and Pudding Stones next summer when I go to the U.P. Wish me luck!!