Yes, quartz is naturally occurring silica though it is often impure.
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during heat prusure and time it changers from quartz to smoky quartz
Quartz is a mineral not a rock. Fossils can be found associated with quartz in sedimentary rock not inside the quartz.
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Specific gravity of quartz > 2.65; variable 2.59-2.63 in impure varieties.
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The answr is agate
Impure copper is purified by the process called electrolysis.
Each mineral has a unique composition and definite set of properties. Often an alternate may be found for some of these properties. For example there are many piezoelectric materials that will substitute for quartz in some applications.
Quartz, SiO2 has a s.g. of 2.65 if pure, and slightly lower if impure.
An unhealthy or impure water supply is contaminated.
Recrystallized limestone is generally called marble. Recrystallized quartz sandstone is generally called quartzite. There is no such thing as quartz limestone.
bull quartz is SiO2 (quartz) with no appreciable economic elements -- in other words uneconomic quartz
An impure substance can be called a mixture. It could be either heterogeneous mixture or homogeneous mixture.
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Rutilated quartz.