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What Is Dacite?
Dacite is a fine-grained igneous rock that is normally light in color. It is often porphyritic. Dacite is found in lava flows, lava domes, dikes, sills, and pyroclastic debris. It is a rock type usually found on continental crust above subduction zones, where a relatively young oceanic plate has melted below. Composition of Dacite A generalized mineral composition for dacite is intermediate between rhyolite and andesite. It…
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What is Basalt?
Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. It has a composition similar to gabbro. The difference between basalt and gabbro is that basalt is a fine-grained rock while gabbro is…
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What are Igneous Rocks?
Igneous rocks are formed from the solidification of molten rock material. Some form below Earth’s surface. Some form on or above Earth’s surface. We describe these two basic types: Intrusive igneous rocks crystallize below Earth’s surface, and the slow cooling that occurs there allows large crystals to form. Examples of intrusive igneous rocks are: diabase, diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous…
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Minerals: The Keys to Coloring Glass
The sources of the oxides, sulfides, and other metallic compounds used to color glass are minerals. These minerals are typically mined, processed to remove impurities, and used to manufacture coloring agents for glass. The keys to beauty often come right from the Earth.
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Widely Known Glass Colors
Some colors of glass are widely known. Perhaps the best example of this is “cobalt blue” that is produced by adding cobalt oxide to the glass melt. “Vaseline glass” is a fluorescent yellow-green glass that contains small amounts of uranium oxide. “Ruby gold” and “cranberry glass” are red glasses produced by the addition of gold.…
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Metals Used to Color Glass
The recipe for producing colored glass usually involves the addition of a metal to the glass. This is often accomplished by adding some powdered oxide, sulfide, or other compound of that metal to the glass while it is molten. The table below lists some of the coloring agents of glass and the colors that they…
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Colors of Duration
Then, another problem was discovered. Many of the glass colors did not stand up to year-in, year-out exposure to the direct rays of the sun. The result was a stained glass scene of deteriorating beauty. Some colors darkened or changed over time, while others faded away. Red, a very important color for use in a…
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The Glass Color Palette
Once the methods of colored glass production were discovered, an explosion of experimentation began. The goal was to find substances that would produce specific colors in the glass. Some of the earliest objects made from glass were small cups, bottles, and ornaments. Religious organizations were among those who provided incentive to the early glass artisans.…
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The Colored Glass Recipe
The earliest people who worked with glass had no control over its color. Then, through accident and experimentation, glass makers learned that adding certain substances to the glass melt would produce spectacular colors in the finished product. Other substances were discovered that, when added to the melt, would remove color from the finished project. Egyptian…
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Color: The Most Obvious Property of Glass
Color is the most obvious property of a glass object. It can also be one of the most interesting and beautiful properties. Color sometimes defines the usefulness of a glass object, but it almost always defines its desirability.