Questionaire 3 (A3CS)
Needles of actinolite found in emerald are classified as
inclusions
If a crystal grows in a flux that is highly saturated with the necessary elements, it tends to be
small - The degree of saturation of nutrients as well as the cooling time are important factors that ecide the number and size of rystals that grow in an environment.
Rough spinel often occurs as
twinned crystals - look as if the crystal was twisted around a plane at its center.
Which gems are cryptocrstalline aggregates
Chalcedony and turquoise - Made up of tiny individual crystals.
Which element caused red in ruby and green in emerald?
Chromium - caused some of the most valuable colors in gems.
Which type of twinning looks as if two crystal halves are mirror images?
Contact.
Which aggregate's crystals are visible only with magnification greater than a standard gemological microscope's
Cryptocrystalline
An object's weight in relation to its size is called its
Density
The trace elements that cause corundum's blue are
Iron and Titanium
A two-phase inclusion is a cavity in a gem thats typically filled with a
Liquid and a gas.
Which type of twinning is caused by environmental change after the gem forms?
Polysynthetic- or lamellar twinning is a type of secondary twinning that occurs after the gem has formed when the rocks it formed in are altered by pressure from metamorphism.
Which is classified in the orthohomic crystal system?
Topaz - The structure of topaz's unit cell places this mineral in the orthorhombic crystal system. Garnet is cubic, beryl is hexagonal, and corundum is triagonal.
Atoms in a gem that are not part of it's essential chemical compostions are
Trace elements.
A unit cell defines a mineral's
arrangment of the atoms in the chemical composition
Many fashioned rubies have shallow proportions because they're cut from
flat crystals- the shape of the rough determines the shape of the finished gem. many fashioned rubies have shallow proportions due to the flat rough the cutter had to work with.
