Geo midterms

• Mineralogy is concerned with all aspects of mineral.
• Mineral is a naturally solid and inorganic substance which forms the earth.
• Smoky Quartz is a mineral that is composed of silicon and oxygen (SiO2).
• Crystalline structure means that the atoms inside the mineral are arranged in a symmetrical manner.
• Obsidian is also called as volcanic glass and has no internal structure. It is not considered a mineral.
• Fixed or variable chemical composition means that each mineral has its own chemical composition.
• Quartz in the form of amethyst has a fixed chemical composition.
• Color should not be relied upon.
• Luster is how the surface of the mineral reflects light.
• Streak is the color of the mineral as a powder.
• Cleavage is the direction of the weakness of a mineral.
• Fracture is the breakage of the mineral.
• Hardness is the strength of the mineral to resist scraping and puncture.
• Talc is the softest mineral.
• Diamond is the hardest mineral.
• Crystal shape means that all minerals are crystalline but some doesn't have the opportunity to show their crystal form.
• Acid reaction distuingish small number of minerals with some properties.
• Magnetism is the reaction when a small magnet reacts to the mineral.
• Magnetite is the most common mineral that is magnetic.
• Specific gravity is the density of the mineral.
• Feldspar is the most abundant group of minerals on earth.
• Petrology is the study of rocks.
• Igneous rocks are formed by solidification of molten magma.
• Aphanitic fine-grained, less than 1mm, grains not seen with the unaided eye.
• Phaneritic coarse-grained, visible crystal and 1 to 10 mm.
• Pegmatitic very coarse grained, 1 cm.
• Porphyritic composed of both large and fine-grained crystals.
• Vesicular rocks that have vesicles resembling a sponge.
• Pyroclastic fragmented angular grains ejected during the eruption.
• Glassy when lava cools quickly.
• Intrusive igneous rocks crystallize below the earth's surface.
• Extrusive igneous rocks erupt into the surface resulting in small crystals as the cooling take place quickly.
• Granite is a hard igneous rock made of clearly visible crystals of various minerals.
• Basalt is a dark-colored fine-grained igneous rock.
• Pumice is a light igneous rock with thousands of tiny bubbles.
• Sedimentary rocks are from pre-existing rocks or pieces of once living organisms.
• Clastic sedimentary rocks are from accumulation and lithification of mechanical weathering debris.
• Chemical sedimentary rocks form when dissolved materials precipitate from solutions.
• Organic sedimentary rocks form from accumulation of plant or animals debris.
• Metamorphic rocks have been modified by heat, pressure, and chemical process.