I was given a crossword puzzle to help study for my upcoming igneous petrology e

Question

I was given a crossword puzzle to help study for my upcoming igneous petrology exam. These are the only words I can't figure out.

1) A mineral grain that formed early in the crystallization history of an igneous rock: _ _ E _ _ _ R _ _ _ (10 letter word) (Pretty sure it's Olivine but that doesn't fit and I already used it for another clue)

2) Adding water into a silicate melt can decrease: _ _ _ _ _ _ i _ _ (8 letter word) (I know it lowers the melting temp but I can't figure out the one word)

3) A mineral you must find in alkali basalt: _ _ _ _ _ _ _ _ _ (9 letter word)

4) Minerals with tetragonal and hexagonal symmetry are optically: _ _ _ A _ _ A _ (8 letter word)

5) Ocean island generally form above these features: _ _ _ _ _ _ T (7 letter word) (I think it's hotspot)

6) The magma of alkaline series first show the enrichment of: _ _ _ _ (4 letter word) (I think its LREE)

Explanation / Answer

1) Phenocryst . A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock.

2) viscosity ( its 9 letter word , as there are space for 9 letters) . Adding water deceases the polymerization of silica by breaking silica bonds and hence decreasing the viscosity of a silicate melt.

3) Nepheline , It is evident through basalt tetrahedron classification .

4) Uniaxial , Uniaxial minerals are a class of anisotropic minerals that include all minerals that crystallize in the tetragonal and hexagonal crystal systems.  They are called uniaxial because they have a single optic axis.

5) yes , Hotspot . At the position directly over the hotspot, rising mantle melts to produce magma that erupts on the seafloor, eventually building a volcanic island directly over the hot spot. As the lithospheric plate moves over the hot spot the volcano eventually is cut off from its source of magma, and becomes extinct, and a new volcano forms on the plate at the location directly above the hot spot. Hawaii is the best example of ocean island

6) LREE or ( It can also be iron enrichment as the basis of classification is iron)

Different groups of alkaline rocks are enriched in specific incompatible trace elements and may also show either prevalence of Na over K or vice versa.Alkaline rocks may comprise several volumetric per cent or more of minerals containing essential Zr, , Nb, Sr, Ba, or Li

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