Radioactive Decay, Rocks, and Mineral Notes for test on 1/20/2026

What is a mineral?

A mineral is a naturally formed, inorganic solid with a crystalline structure.

What are the four criteria that define a mineral?

It must be a solid, naturally occurring, inorganic, and have a crystalline structure.

What is the difference between minerals and rocks?

Rocks are made of many minerals, but minerals are not made of rocks.

What is the physical property of color in minerals?

Color does not provide much information about the mineral.

What does luster refer to in minerals?

Luster describes how a mineral reflects light, categorized as metallic or non-metallic.

How is the streak of a mineral determined?

The streak is the color of the mineral in powdered form, found by rubbing it on a porcelain streak plate.

What is the difference between cleavage and fracture in minerals?

Cleavage is the tendency to break along smooth planes, while fracture is uneven or irregular breaking.

What scale is used to measure the hardness of minerals?

The Mohs' Hardness Scale.

What is density in terms of minerals?

Density is the mass of a mineral divided by its volume (D=m/v), unique to each mineral.

What are some special properties of minerals?

Fluorescence, optical properties, radioactivity, magnetism, taste, and reactions to chemicals.

What is an igneous rock?

An igneous rock forms from the cooling and solidification of magma or lava.

What are the two types of igneous rocks based on cooling location?

Intrusive (plutonic) rocks cool inside the Earth, while extrusive (volcanic) rocks cool on the surface.

What is lithification in sedimentary rocks?

Lithification is the process of compaction and cementation that turns sediment layers into rock.

What are clastic sedimentary rocks?

Rocks formed from weathered rock fragments that are transported and deposited.

What is the difference between chemical and organic sedimentary rocks?

Chemical rocks form from dissolved materials, while organic rocks form from once-living organisms.

What characterizes metamorphic rocks?

Metamorphic rocks have changed due to extreme heat and pressure without melting.

What is contact metamorphism?

Metamorphism that occurs due to heat from an igneous intrusion.

What is regional metamorphism?

Metamorphism caused by heat and pressure from tectonic plate movements.

What is thermal convection in the Earth's mantle?

The movement of mantle material due to heat causing less dense material to rise and cooler material to sink.

What is a half-life in radioactive decay?

The time it takes for 50% of unstable parent atoms in a sample to decay into stable daughter atoms.

How does the half-life of Uranium-238 compare to Carbon-14?

Uranium-238 has a half-life of about 4.5 billion years, while Carbon-14 has a half-life of 5,730 years.

What is the significance of measuring parent to daughter atom ratios in geology?

It allows geologists to determine the age of rocks and understand Earth's formation history.

What is the highest temperature at which magma crystallizes?

1400°C.

What is the lowest temperature at which the cooling process of magma ends?

650°C.

What does it mean for a rock to be felsic?

A felsic rock has a high content of silica, potassium, and sodium.

What does it mean for a rock to be mafic?

A mafic rock has a high content of iron, magnesium, and calcium.