IUGS Classification Coarse Grain/ Texture

Question 1

Quartz compromise more than 90% of the felsic minerals, and has <90% mafic minerals. It may be hydrothermally altered granitoids (e.g. greisen)

Answer 1

Quartzolite

Question 2

A light colored mineral where plagioclase is less than 10% of the total feldspar.

Answer 2

Alkali-feldspar granite

Question 3

An alkali-feldspar/ total feldspar ratio from 0.35-0.90 on the QAFP diagram and 20 - 60% quartz

Answer 3

Granite

Question 4

An alkali-feldspar/ total feldspar ratio from 0.65 - 0.90 and 20 - 60 quartz

Answer 4

Syenogranite

Question 5

An alkali-feldspar/ total feldspar ratio from 0.35-0.65 on the QAFP diagram. Often called adamellite.

Answer 5

Monzogranite

Question 6

It has 20-60% quartz and a plagioclase of 65-90% of the total feldspar.

Answer 6

Grandiorite

Question 7

A granitoid, where plagioclase is >90%

Answer 7

Tomalite

Question 8

Plagioclase is less than 10% of the total feldspar

Answer 8

Alkali-feldspar syenite

Question 9

No quartz and containing up to 10% foids

Answer 9

Foid-bearing alkali feldspar syenite

Question 10

Alkali-feldspar/ plagioclase ratio from 65-90% and <5% quartz. Intrusive equivalent of ‘trachyte’

Answer 10

Syenite

Question 11

No quartz and <10% foids

Answer 11

Foid-bearing syenite

Question 12

Equal amounts of alkali feldspar and plagioclase, and thus intermediate between diorite and syenite. Intrusive equivalent og latite.

Answer 12

Monzonite

Question 13

Dioritic rock with <5% quartz and 10-35% alkali feldspar on the QAFP diagram.

Answer 13

Monzodiorite

Question 14

A syenitoid with 5-20% quartz and subequal K-feldspar and plagioclase (35-65% of the feldspar being plagioclase). Coarse-grained equivalent of quartz-latite.

Answer 14

Quartz-monzonite

Question 15

Less than 5% quartz or no foids, and no 10-35% K-feldspar.

Answer 15

Monzogabbro

Question 16

Dioritic rock with 5-20% quartz and 10-35% alkali feldspar.

Answer 16

Quartz monzodiorite

Question 17

More than 5% quartz and 10-35% K-Feldspar

Answer 17

Quartz monzogabbro

Question 18

Foid-dioritoid where K-feldspar is >50-10% of feldspar

Answer 18

Foid monzodiorite

Question 19

Foid gabbroic rock where plagioclase is 50-90% of feldspar

Answer 19

Foid monzogabbro

Question 20

<5% quartz and <10% alkali feldspar on the QAFP diagram

Answer 20

Diorite

Question 21

Composed of 10-90% Ca-dominant plagioclase and >5% clinopyroxene

Answer 21

Gabbro

Question 22

Mostly of calcic plagioclase (>90% usually labradiorite) with <10% mafics

Answer 22

Anorthosite

Question 23

Dioritic rock with 0-10% quartz and 10-35% alkali feldspar.

Answer 23

Quartz Diorite

Question 24

Gabbro with felsic minerals comprising more than 5% quartz

Answer 24

Quartz Gabbro

Question 25

Diorite with <10% foids and <10% alkali feldspar

Answer 25

Foid-bearing diorite

Question 26

Gabbro containing up to 10% foid minerals

Answer 26

Foid-bearing gabbro

Question 27

Rock where K-feldspar is >90%

Answer 27

Foid syenite

Question 28

Foid-syenitoid where K-feldspar is >50-90% of feldspar

Answer 28

Foid monzosyenite

Question 29

Foid-dioritoid where k-feldspar is 50-90%

Answer 29

Foid monzodiorite

Question 30

Plagioclase is >90% of feldspar

Answer 30

Foid diorite

Question 31

Rock with <90% mafics, >60% of felsic being foids

Answer 31

Foidolite

Question 32

Minerals consisting of aluminosilicates of sodium, potassium, or calcium and having too little silica to form feldspar.

Answer 32

Foids (feldspathoids)

Question 33

and Enumerate the common foid mineralss

Answer 33

Analcime
Leucite
Nepheline
Sodalite

Question 34

Crystals visible to the naked eye.

Answer 34

Phaneritic

Question 35

Crystals so small that they cannot be seen with the naked eye

Answer 35

Aphanitic

Question 36

Composed entirely of crystals

Answer 36

Holocrystalline

Question 37

Composed entirely of glass

Answer 37

Holohyaline

Question 38

Composed of crystal and glass

Answer 38

Hypocrytalline

Question 39

Phenocrysts set in a glassy groundmass

Answer 39

Vitrophyric

Question 40

Phenocrysts containing numerous inclusion of another mineral that they enveloped with growth.

Answer 40

Poikilitic

Question 41

Host crystal of poikilitc is termed as _________.

Answer 41

Poikilitc

Question 42

Holes in the rock formed by escaping gases during solidification

Answer 42

Vesicle

Question 43

Result of rapid growth of olivine and develop elongated olivine crystals

Answer 43

Spinifex texture

Question 44

Nucleation of one mineral on a preexisting mineral e.g. growth of sillimanite on biotite or muscovite

Answer 44

Epitaxis texture

Question 45

Plagioclase overgrowths on orthoclase (K-feldspar)

Answer 45

Rapakivi texture

Question 46

In silicic volcanic rocks in which needles of quartz and alkali feldspar growth radially from a common center

Answer 46

Spherulitic texture

Question 47

Refers to the envelopment of plagioclase laths by larger larger clinopyroxene and is commonly interpreted to indicate that clinopyroxene formed later.

Answer 47

Ophitic texture

Question 48

Radiating plagioclase laths in some basalts are probably the result of nucleation of later crystals on the first nuclei to form during devitrification of glass

Answer 48

Variolitic texture

Question 49

Evidence for advanced resorption, or rapid growth enveloping melt due to undercooling

Answer 49

Sieve texture

Question 50

Result from simultaneous crystallization of feldspar and quartz, the intergrowth forms epitaxially preexisitng phenocrysts or dikelet walls

Answer 50

Granophyre and Graphic Texture