EnchantedLearning.com Rock and Mineral Dictionary

salt Salt (NaCl or sodium chloride) is a crystalline chemical that occurs naturally around the world, in oceans and in salt deposits. The oceans on Earth contain salt (roughly 2.6% salt by weight), as do some lakes. The mineral halite, formed of NaCl, is a colorless to gray to brown crystal. Salt has a hardness of 2.5 and a specific gravity of 2.165. Its index of refraction is 1.5442. NaCl melts at 800.0 °C and boils at 1,465 °C. In solution (dissolved in water), salt is neutral (it is neither acidic nor basic).

sand Sand is a loose material composed of fine debris of rock and mineral particles (usually geology/rocks/glossary/indexq.shtml" target="_top">quartz) that are from 0.0625 to 2.0 millimeters in diameter.

sandstone Sandstone is a common type of grainy sedimentary rock that is made mostly of sand-sized grains (usually quartz) that are held together by silica, calcium carbonate, clay, or iron oxide.

sapphire Sapphire is a precious gemstone (a type of corundum) that ranges in color from blue to pink to yellow to green to white to purple (mauve sapphire) to pink-orange (padparadscha sapphire). Six-sided asterisms sometimes occur in star sapphires (caused by inclusions of tiny, thin, parallel needles of rutile). Sapphires are related to rubies. Sapphires were once thought to protect the wearer from poisonous creatures. Sapphire has a hardness of 9 and a specific gravity of 3.9 - 4.1. Sapphires are often heat treated to improve their color.

sapphire quartz Sapphire quartz (also called blue quartz) is another name for blue chalcedony.

sard Sard is a semi-precious stone related to carnelian. This brownish-red, opaque gemstone was once used extensively for seals and was carved using intaglio. Sard was named for Sardis, the ancient capital of Lydia. Sardius is mentioned in the Bible, and may refer to jasper.

sardonyx Sardonyx is a semi-precious stone that is formed by two layers, a red-brown layer of sard and a gray, white, black or brown layer of onyx. Sardonyx is a type of quartz. Sardonyx is frequently carved to make intricate cameos and seals.

scarp A scarp (also called an escarpment) is a cliff or row of cliffs that were formed by formed by faults in the crust, erosion, or landslides.

schiller Schiller (from the German term for play of colors or glitter) is an iridescent or bronze-like luster occuring in some minerals (it is also referred to as labradorescence when it occurs in feldspars). This optical effect is caused by submicroscopic lamella (thin layers or flakes of inclusions) contained within the mineral. These layers of inclusions can produce a bronze-like luster, golden iridescence, red color-play, and/or a blue-green sheen that flashes when viewed from certain angles. This type of inclusion can be valuable (as in sunstone and labradorite). Layers of shiller can block reflected light, decreasing the stone's brightness. Some types of feldspars (like labradorite, sunstone, spectrolite and peristerite) and other minerals (like hypersthene) exhibit schiller.

schist Schist is a type of crystalline metamorphic rock whose consistuent grains are in an organized pattern. Schist is formed from fine-grained sedimentary rocks like shale.

science People study science to learn about the physical world.

scoria Scoria are bomb-sized (greater than 64 mm across) pyroclastic fragments that are formed as blobs of lava cool when they are blasted through the air. Scoria are filled with cavities formed by trapped air bubbles.

seafloor spreading Seafloor spreading is the movement of two oceanic plates away from each other, which results in the formation of new oceanic crust and a mid-ocean ridge.

sea glass Sea glass (also called beach glass) is glass from old broken bottles, windows of wrecked ships, etc. that has been worn down and etched by the sea and sand over the years. This glass is smooth (with no sharp edges) and looks like beautifully sand-blasted glass with a soft patina. Pieces of this glass are collected on beaches and often made into jewelry items. Brown, deep green and clear are the most common colors of sea glass; after these come blue, amber and aqua. Rare colors include pink, red, purple, light yellow, and sea green.

seamount A seamount is an underwater mountain that rises at least 50-100 m above the sea floor. Some seamounts rise above the water's surface. Most seamounts are volcanic in orgin; only a few are non-volcanic (caused by uplifting).

sediment Sediment is loose mineral or biologic material that is deposited by water, ice, or air.

sedimentary rock Sedimentary rock is rock that has formed from sediment, like sand, mud, small pieces of rocks. Over long periods of time, these small pieces of debris are compressed (squeezed) as they are buried under more and more layers of sediment that piles up on top of it. Eventually, they are compressed into sedimentary rock. It is made of strata, or layers. The layers that are farther down in the Earth are older than the top layers. Most fossils are found in sedimentary rock. sandstone, shale, and limestone are sedimentary rocks.

seftonite Seftonite is a translucent, moss green type of chalcedony. It is found in South Africa and North America.

sky The sky on Earth appears blue because our atmosphere scatters the blue colors from the sunlight (which consists of all colors of light). The sky on planets with a different atmospheric composition would appear to be a different color.

smoky quartz Smoky quartz is a type of brownish quartz that has a smoky look.

snowflake obsidian Snowflake obsidian (also called flowering obsidian) is a volcanic glass that is usually dark (black or brownish) with white "snowflakes". This glassy, lustrous mineral is found in lava flows, and obsidian stones can be massive. Obsidian is formed when viscous lava (from volcanos) cools rapidly. Most obsidian is 70 percent silica. Obsidian has a hardness of 5 and a specific gravity of 2.35.

soapstone Soapstone (also called steatite) is a soft, easily-carved, fine-grained metamorphic rock that can be green, brown, or gray. This stone has a greasy, soapy feel to it, hence its name. Soapstone is found worldwide. It is carved into figurines, beads, seals, bowls, pipes, cookware, and other items - it has been used since ancient times. Chemically, soapstone is composed mostly of talc, hydrated magnesium silicate (Mg3Si4 O10(OH)2) plus other minerals. Soapstone has a hardness of 1-1.5 (extremely soft - it can be scratched with a fingernail) and a specific gravity of 2.2-2.8.

sodalite Sodalite is a dark blue mineral with streaks of white, gray, pink, or green. It is used for carvings and jewelry. Sodalite is one of the mineral components of lapis lazuli. . Sodalite is sodium aluminum silicate chloride; its formula is Na4Al3(SiO4)3Cl. Sodalite has a hardness of 5.5 to 6 and a specific gravity of 2.1 - 2.3. Sodalite is found in Brazil, Canada, India, Italy, Namibia, United States, and Russia.

soil Soil is a natural, constantly-changing substance that is made up of minerals, organic materials, and living organisms. plants grow in soil.

soil horizons Soil is made up of distinct horizontal layers; these layers are called horizons. They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock).

states of matter Matter can exist in four states or phases (solid, liquid, gas, and plasma) and a few other extreme phases (like critical fluids and degenerate gases). The phase diagram of water (above) shows its phase at various temperatures and pressures.

steatite Steatite (also called soapstone) is a soft, easily-carved, fine-grained metamorphic rock that can be green, brown, or gray. This stone has a greasy, soapy feel to it, hence its name. Soapstone is found worldwide. It is carved into figurines, beads, seals, bowls, pipes, cookware, and other items - it has been used since ancient times. Chemically, soapstone is composed mostly of talc, hydrated magnesium silicate (Mg3Si4 O10(OH)2) plus other minerals. Soapstone has a hardness of 1-1.5 (extremely soft - it can be scratched with a fingernail) and a specific gravity of 2.2-2.8.

stishovite Stishovite is a very dense form of quartz that has only been found in meteorite impact craters, in which quartz has undergone high-pressure shock.

subduction A subduction is a phenomenon in which one part of the Earth's crust (a plate) is pushed underneath another plate as two plates collide. The descending crust melts as it is pushed deep into the Earth's mantle. Subduction destroys crust and recycles it back into the mantle.

subduction zone A subduction zone is an area on a planet's crust in which the edge of an oceanic continental plate is being pushed beneath another plate.

sublime Subliming is when a material goes directly from being a solid to being a gas (it skips the liquid phase altogether).

Suess, Eduard Eduard Suess was an Austrian geologist who first realized that there had once been a land bridge between South America, Africa, India, Australia, and Antarctica. He named this large land mass Gondwanaland (named after a district in India where the fossil plant Glossopteris was found). This was the southern supercontinent formed after Pangaea broke up during the Jurassic period. He based his deductions upon the fossil fern Glossopteris, which is found throughout India, South America, southern Africa, Australia, and Antarctica.

sugilite Sugilite is a medium to dark purple semi-precious gemstone (it can also range from pink to brown to black). It is usually opaque with a waxy luster (but can be translucent) and often has brown, pink and white inclusions, looking like a purple version of turquoise. It is usually polished and not faceted. Sugilite has a hardness of 5.5-6.5 and a specific gravity of 2.75 - 2.80. This stone is not enhanced - massive stones are often found. Sugilite is Potassium Sodium Lithium Iron Manganese Aluminum Silicate; its formula is KNa2Li3(Fe, Mn, Al)2Si12O30. This stone was named for Ken-ichi Sugi, the Japanese geologist who discovered it in 1944. It is found in Iwagi Island, Shikoku, Japan and Mont Saint-Hilaire, Quebec, Canada, but the largest deposits are in northern South Africa.

sunstone Sunstone is also called aventurine feldspar (a variety of oligoclase). This gemstone varies from golden to orange to red-brown, and can be transparent or translucent. Sunstone is metallic-looking due to sparkling red, orange or green crystalline inclusions (these are hematite or goethite crystals). Sunstone is found in Canada, the USA (in Oregon), India, Norway, and Russia. This brittle stone has a hardness of 6 and a specific gravity of 2.63 - 2.67. Sunstone is not enhanced.

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