EESB15 - Earth History Course: 4.5(6) Billion Years - The Big Riddle

Vocabulary flashcards covering key Earth history and mineralogy concepts from Lecture 1.

Precambrian era

The interval of Earth's history before the Cambrian period; includes the planet's formation and earliest rocks and life.

Cretaceous period

A period of the Mesozoic Era (~145–66 million years ago) ending with a mass extinction that wiped out many dinosaurs.

Mesozoic era

Geologic era between the Paleozoic and Cenozoic; known as the Age of Dinosaurs; includes Triassic, Jurassic, and Cretaceous.

Triassic period

First period of the Mesozoic Era (about 252–201 million years ago).

Permian period

Last period of the Paleozoic Era (about 299–251 million years ago); ended with a major mass extinction.

Jurassic period

Middle of the Mesozoic Era (about 201–145 million years ago); famous for dinosaurs.

Pennsylvanian period

Late Carboniferous subperiod (roughly 323–298 million years ago); coal-forming forests in some regions.

Mississippian period

Earlier Carboniferous subperiod (roughly 359–323 million years ago); significant carbonate reefs and coal measures.

65 million years ago

Time at which the Cretaceous ended; mass extinction that included non-avian dinosaurs.

Mohs scale

Relative scale (1–10) of mineral hardness used to compare scratch resistance.

Mineral

A naturally occurring, inorganic, solid crystalline substance with a definite chemical composition and orderly atomic arrangement.

Quartz

A common silicate mineral (SiO2) with hardness 7; color ranges from clear to colored; widespread in rocks.

Halite

Sodium chloride (NaCl); rock salt; forms cubic crystals; hardness about 2–3.

Muscovite

A light-colored mica with perfect basal cleavage into thin, flexible sheets; hardness ~2–2.5.

Biotite

A dark mica (mica group); brown-black color; cleavage; hardness ~2.5–3.

Plagioclase

A plagioclase feldspar; hardness ~6–6.5; two-direction cleavage; typically white to gray.

Orthoclase

Potassium feldspar; hardness ~6; two-direction cleavage; pink to white in color.

Olivine

Ferromagnesian silicate mineral; olive-green color; hardness ~6.5–7; SG ~3.2–3.6; common in mafic rocks.

Pyroxene

Ferromagnesian silicate mineral; hardness ~5–6; two-direction cleavage at ~90°; dark green to black.

Amphibole

Ferromagnesian silicate with hardness ~5–6; cleavage at ~60° and 120°; often dark colored.

Garnet

Silicate mineral; hardness ~6.5–7.5; typically red, brown, or yellow; commonly occurs in dodecahedral crystals.

Euhedral

Well-formed crystal faces from ample space to grow; conspicuous crystal outlines.

Anhedral

Crystal forms lacking well-developed faces due to restricted growth space.

Streak

Color of a mineral's powder when rubbed on a porcelain plate; can help identification.

Luster

How a mineral reflects light; metallic vs non-metallic; dull, glassy, or pearly appearances.

Cleavage

Tendency of a mineral to break along planes of weakness; described by direction and angle.

Fracture

Breakage of a mineral not along cleavage planes; includes conchoidal fracture.

Conchoidal fracture

Curved, shell-like fracture surface seen in glasses and minerals like quartz.

Tenacity

A mineral's resistance to breaking, bending, or deforming; includes brittle, ductile, and malleable.

Crystal habit

The external shape of a crystal; includes euhedral vs anhedral forms.