24 specimens, 1 1/4", including six each of the following: rock-forming minerals, igneous, sedimentary and metamorphic rocks. Also includes a study guide.
ROCK AND ROCK-FORMING MINERALS
Minerals are naturally occurring chemical compounds or elements found in the earth's crust and are the building blocks of rocks. Rocks may contain only a single mineral, but usually they contain a mixture of many minerals.1. Quartz - Silicon dioxide, or quartz, is the most common mineral in the earth's crust.
Igneous rocks were once lava or magma, that is, a molten collection of minerals. The rate at which a lava or magma cools and solidifies influences rock texture, making it either fine, medium or coarse grained.7. Pumice - A light colored volcanic rock of rhyolitic composition; the texture results from bubbles formed by escaping gasses.
Metamorphic rocks are rocks that have been changed (metamorphosed), by heat, pressure, and/or hydrothermal solutions. All three rock types can be metamorphosed.13. Mica Schist - This rock is a highly metamorphosed shale. All schists exhibit shistose structure; the generally parallel alignment of micaceous minerals.
Clastic sedimentary rocks are formed from layers of sediment (fragments of older, weathered rock) exposed to pressure. Other sedimentary rocks are of organic or chemical origin.19. Sandstone - Quartz grains cemented together by silica, calcite or other cementing minerals make up this clastic, sedimentary rock.
The Mineral Hardness Ruler is a stimulating visual aid, educates in one phase of mineralogy, and provides the standard ruler measurement scales needed in classes.
Rockhounds, mineral enthusiasts, students, teachers, geologists, and any one interested in rocks and minerals will find the Mineral Hardness Ruler a handy visual aid for quick information on mineral hardness.
The two-sided, flexible, glossy, vinyl ruler consists of five scales: three measurement scales and two mineral hardness scales. The measurement scales are in standard ruler measurements of tenths of inches, sixteenths of inches, and millimeters. Mohs' relative hardness numbers are integrated into the inch scales, while a separate scale exists for an absolute mineral hardness scale by Rosiwal.
On one side of the ruler are pictures of the ten common minerals, in full color, selected by Mohs for his relative hardness scale. On the reverse side of the ruler are six common items with their relative hardnesses. These items, along with known minerals, can be used as a handy field kit to test the relative hardness of an unknown mineral.
Hardness is one property of a mineral that can be used to distinguish among similar minerals. A given mineral can scratch any other mineral of the same or softer hardness. Over a hundred years ago, the German mineralogist Frederick Mohs devised the relative hardness scale that has found favor with mineralogists for over a century. Others, such as Rosiwal, formed absolute hardness scales using the same minerals as Mohs. For example, diamond, the hardest substance in Nature is not twice as hard as apatite, 10 versus 5, but over twenty thousand times as hard, 140,000 versus 6.5.
This is a great little pocket guide to rocks and minerals. It uses color drawings to illustrate the rocks and minerals which I find is far more handy that pictures of museum quality specimens. Rocks and minerals in the field often don't know what they're supposed to look like so they are more average than those museum exhibits!
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