Questionaire 2 (A2CS)
Which is a key locality for hydrothermal gems?
Ouro Preto, Brazil - Imperial topaz from Brazil and emeralds from Columbia are important hydrothermal gems.
Which gem forms by metamorphism?
Tanzanite - The metamorphic rocks of Easy Africa produce as well as ruby, emerald, alexandrite, and tsavorite, among others.
Which is a deposit where gems eroded from the source rock and remained in place nearby?
Eluvial
Most gemstones form in the
continental crust. - contains the right conditions for formation.
Heat and pressure transform limestone into
Marble- The limestone deposits of Mogok, Myanmar, are converted to marble by heat and pressure.
Which is a workable alluvial deposit of gem minerals with economic potential?
Placer
Which gem can crystallize in volcanic rock from gasses released by magma?
Red beryl - both red beryl and topaz
Which type of deposit is usually the most profitable for colored stone mining?
Secondary - Erosion has done some of the work for miners of secondary deposits usually making it more profitable.
Pegmatite gems are rich in volatile elements like
beryllium, boron, and lithium.
Rocks altered by heat and pressure are
metamorphic - transform rocks into new rocks.
Most of the gems in Tanzania's Umba River Valley are found in
placer deposits
A deposit where gems are found in the rock that directly carried them to the earth's surface is called
primary
Myanmar's famous Mogok ruby deposits were formed by
regional metamorphism - in limestone altered to marble.
Kunzite is most often found in association with
tourmaline and beryl in pegmatite. - and kunzite are all found in association with pegmatite.
Emeralds are rarely found in placer deposits because they're
unable to withstand much abrasion - Emeralds are often damaged by the transportation that takes place in the creation of a placer deposit.
