Rock Hardness Scale

Hiking Petrified Forest

Twenty miles east of Holbrook, Ariz., travelers along Interstate 40 can leave the highway and delight in a truly remarkable wonder of nature.

Allowed time, conditions and a blend of minerals, a magical transformation occurs. A tree turns into stone. Petrified Forest National Park, encompassing 50,260 acres, gained park status in 1962. Containing one of the world’s largest concentrations of petrified wood, Arizona’s national park also claims the most colorful. Found in nearly every one of the United States, this material is also encountered in dozens of countries around the world.

Generally, it takes less than 100 years to petrify wood. Preserved underground without oxygen, mineral-laden water seeps through the sediment, depositing minerals in the organic plant cells and converting them to stone.

The primary geological formation in Petrified Forest National Park is the Chinle Formation, deposited more than 200 million years ago, during an era known as the Triassic Period. This region was situated slightly north of the Equator. In that tropical climate huge coniferous trees flourished. Once they fell, massive flooding moved the logs downstream, ending up in immense logjams. Buried beneath sediment, a century later these logs would petrify.

With the movement of the earth’s crust, this region moved gradually far to the northwest, eventually to its current location in Arizona. About 60 million to 80 million years ago the Colorado Plateau began to uplift. Erosion removed rock layers, exposing the petrified forest. Plant and animal fossils as well as tons of petrified wood still lie buried below the surface.

A 28-mile drive through the park provides an opportunity to view up close the results of this magical process, named petrification. Thousands of tons of beautifully colored logs lie across grassy fields and beside low hills of Bentonite clay. A softball-sized piece weighs as much as a shot-put. Petrified wood is also extremely hard. On the Mohs’ scale of hardness it ranks at 7.8. Talc is a one, diamonds are a 10. Several trails, all paved, wind intimately through lands littered with gigantic stone logs, wonderful examples of nature’s art.

Following a brief stop at the visitor center at the north entrance, wonders of this place quickly unfold at pullouts along the paved road, overlooking a fabulously colored Painted Desert. As thunderclouds fill the horizon sky, bright sunlight washes across the valley, enhancing an already gorgeous setting. Painting a vast array of pastels, pink, red, purple, charcoal, yellow, orange and more, low hills sparkle in afternoon sun. This is Mother Nature in another of her finest hours.

Buy Cheap Mohs Scale of Hardness w/ Diamond Rock Mineral - rc toy

Mohs Scale of Hardness w/ Diamond Rock Mineral Description Quantity:  1 - Scale of Hardness Rock Set with Diamond   This is the traditional Mohs Scale with a small raw diamond included. There are ten number coded specimens measuring approximately 1 x 1 1/2 inches (except the diamond, don't you wish!).  The determination of the hardness of a mineral can be an important step toward its identification.  Hardness is the resistance which the smooth surface of a mineral offers to being scratched.  A diamond is the hardest of all substances and can only be scratched by another diamond.  Over a century ago, Friedrich Mohs by experimentation made up a scale of hardness which is referred to as Moh's scale.  It does not imply an exact hardness, but is set up so that any mineral can scratch all those beneath it in the scale, or can be scratched by those above it in the scale.  Since a diamond is the hardest it is given the number 10; talc is the softest so it is given number 1. Quartz is often used as a division in the scale and all those above 7 are called hard minerals.   Here are the samples included in the set and their number on the scale of hardness: 1 Talc 6 Feldspar 2 Gypsum 7 Quartz 3 Calcite 8 Beryl 4 Fluorite 9 Corundum 5 Apatite 10 Diamond Some very familiar objects can be used in conjunction with this scale.  A fingernail has the hardness of 2.5, a copper coin between 3 and 4, a nail about 5, common window glass 5.5, a steel file or porcelain tile 6.5.  Other minerals are sometimes substituted in the scale such as topaz for beryl since they both have a hardness of 8. Scale of hardness with diamond is recommended for grades 6 to 12. We are also selling this set without the Diamond.

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