Colored Stones 2
Terms
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- A gem produced by, or derived from, a living organism is
- organic
- Which of the following is an organic gem?
- amber
- A Substance that consists of atoms of only one kind is a?
- chemical element
- A natural, inorganic substance with a characteristic chemical composition and usually characteristic crystal structure?
- mineral
- Most gems are?
- minerals
- A natural material that's made up of a mass of one or more kinds of mineral crystals is a?
- rock
- Which of the following is amorphous?
- amber
- A broad gem category based on chemical composition and crystal structure is a?
- gem species
- Which of the following is a gem variety?
- demantoid
- Which group does almandite belong to?
- garnet
- The world's larges gem consuming market is?
- united states
- Compared to the US domestic market for diamonds, the us domestic market for natural, unset, non diamond gems is?
- less than a tenth of the size
- To be a gem, a mineral must be beautiful, durable, and?
- rare
- Many colored stones are mined by?
- independent miners using small scale mining methods
- Media attention in the 1990's regarding its treatment reduced consumer confidence in?
- emerald
- Most gems form in the?
- continental crust
- rocks altered by heat and pressure are?
- metamorphic
- Which gem can crystallize in volcanic rock from gasses released by magma?
- red beryl
- Which is a key locality for hydrothermal gems?
- ouro preto, brazil
- Which gem forms by metamorphism?
- tanzanite
- Heat and pressure transform limestone into?
- marble
- A deposit where gems are found in the rock that carried them to the earth's surface is called?
- primary
- Which type of deposit is usually the most profitable for colored stone mining?
- secondary
- Which is a deposit where gems eroded from the source rock and remained in a place nearby?
- eluvial
- Which is a workable alluvial deposit of gem minerals with economic potential?
- placer
- Kunzite is most often found in association with?
- tourmaline and beryl in pegmatite
- Myanmar's famous Mogok ruby deposits were formed by?
- regional metamorphism
- Pegmatite gems are rich in volatile elements like?
- beryllium, boron, and lithium
- Most of the gems in Tanzania's Umba River Valley are found in?
- place deposits
- Emeralds are rarely found in place deposits because they're?
- unable to withstand much abrasion
- A unit cell deines a mineral's?
- basic identity
- If a crystal grows in a flux that is highly saturated with the necessary elements, it tends to be?
- small
- Which aggregate's crystals are visible only with magnification greater than a standard gemological microscope's?
- cryptocrystalline
- Which is classified in the orthorhombic crystal system?
- topaz
- Which element causes red in ruby and green in emerald?
- chromium
- Which type of twinning is caused by environmental change after the gem forms?
- polysynthetic
- Wich type of twinning looks as if two crystal halves are mirror images?
- contact
- Needles of actinolite found in emerald are classified as
- inclusions
- A two-phase inclusion is a cavity in a gem that's typically filled with a?
- liquid and a gas
- Atoms in a gem that are not part of its essential chemical composition are?
- trace elements
- The trace elements that cause corundum's blue are?
- iron and titanium
- An object's weight in relation to its size is called its?
- density
- Which gems are cryptocrystalline aggregates?
- chalcedony and turquoise
- Rough spinel often occurs as?
- twinned crystals
- Many fashioned rubies have shallow proportions because they're cut from?
- flat crystals
- The pattern of dark lines or bands shown by certain colored gems when viewed through a spectroscope is called?
- absorption spectrum
- Which element does chromium substitute for to cuase ruby's red?
- aluminum
- A gem colored by an element that's part of its basic chemistry is called?
- idiochromatic
- Which element causes the color of both almandite and peridot?
- iron
- The process where electrons that selectively absorb light are passed back and forth between neighboring impurity ions is known as?
- charge transfer
- Which components of a transition element's atoms can produce color in gems?
- electrons
- Which element cuases the finest reds and greens in gemstones?
- chromium
- Which transition element causes more different colors in gems than any other?
- iron
- In many blue sapphires, the intervalence charge transfer that causes the color is between?
- iron and titanium
- When a gem's crystal structure splits light into two rays that each travel at a slightly different speed and direction, it's called?
- double refraction
- What is the only type of gem that can show pleochroism?
- doubly refractive
- Which gem can show three pleochroic colors?
- iolite
- Which phenomenon is a broad color flash?
- labradorescence
- Adularescence is caused by?
- scattering of light
- The best known and most valuable chatoyant gem is cat's eye?
- chrysoberyl
- A laboratory created gem with essentially the same chemical composition, crystal structure, and properties as its natural counterpart?
- synthetic
- Two main types of processes for synthetic gem production are melt and?
- solution
- Low cost and high volume characterize which process?
- flame fusion
- What synthetic process developed rapidly due to laser research in the 1960's?
- pulling
- Which process uses a heating unit to pass over a rotating solid rod of chemicals until it forms a synthetic crystal?
- floating zone
- Which process dissolves nutrients in chemicals to form synthetic?
- flux
- The crucibles that work best for flux growth are made of?
- platinum
- The hydrothermal growth process is the only method used to produce which synthetic gem?
- quartz
- Which synthetic process usses an autoclave?
- hydrothermal growth
- Synthetic opal is grown using microscopic silica spheres that are produced by?
- precipitation
- Which process involves heating finely ground powder, sometimes under pressure, to produce a fine-grained solid material?
- ceramic
- Synthetic turquoise is most likely produced by which process?
- ceramic
- The flux used in the flux process is a solid material that, when molten?
- dissolves other materials
- The hydrothermal synthetic process requires a?
- pressurized steel container and cruhed chemical ingredients
- A snakeskin structural pattern is typical of?
- synthetic opal
- Which is considered a gem treatment?
- fracture filling
- Written information on dyeing gems dates back to about?
- 200 bc
- Which is commonly heat treated?
- amber
- Heat can lighten amethyst's purple by?
- causing changes in color centers
- Creating asterism with heat treatment is most common in?
- synthetic corundum
- What coloring agents do treaters use during surface diffusion to create a shallow layer of blue color in corundum?
- titanium oxide and iron oxide
- How deep is the color layer that surface diffusion creates in corundum?
- 0.01 mm to 0.50 mm
- What agent can treaters intorduce below the surface of a corundum cabochon during surface diffusion to create a shallow layer of asterism?
- titanium oxide
- For effective clarity enhancement, the material used to fill a gem's fractures must have nearly the same?
- refractive index as the gem
- After irradiation, which gem's color is stable under normal wearing conditions?
- golden beryl
- Jadeite is often?
- bleached an polymer impregnated
- The Zachery method is a treatment applied to?
- turquoise
- Heat treatment in a reducing environment?
- deepens blue color in sapphire
- Quartz or topaz with a thin layer of gold deposited on the surface is known as?
- Aqua aura
- Treaters use sugar treatment to enhance?
- opal