Question

Compare rhyolite to basalt (answer in one word only):

a. which has a lower density?


b. which has a lighter color?


c. which has a more mafic composition?


d. which has a greater percentage of biotite in it?


e. which contains quartz? 13. name a felsic, intrusive rock. 14. name a light-colored, plutonic igneous rock.

Answer 1

Rhyolite is a fine-grained igneous rock which is rich in silica while basalt is a common extrusive igneous rock formed by the rapid cooling of basaltic lava exposed at or very near the surface of Earth.
The density of Basalt is higher than that of Rhyolite. Rhyolite has a density that ranges between 2.4-2.6 g/cm^3, while that of Basalt ranges from 2.9-3.1 g/cm^3.

b) Rhyolite is a Grey, white, light black rock, while Basalt is Black, Brown, Light to Dark Grey. Rhyolite appears to be banded while the apperance of Basalt is Dull and soft.

c) Basalt is more mafic; most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, Pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar.

d) Rhyolite has a higher percentage of biotite. Rholite contains a higher percentange of sodium and potassium oxides which can reach up to 5%. Quartz, feldspar and biotite are the most common minerals found in rhyolite. In some cases , thick rhyolitic lavas will cool as glassy obsidian flows.

e) Rhyolite contains quartz. The chemical composition of rhyolite is similar to that of granite. The phenocrysts or rhyolite may include quartz, alkali feldspar, oligoclase feldspar, biotite, amphibole, or pyroxene.

13. I think it is plutonic rocks. Intrusive rocks that were formed deep in the earth's crust are called plutonic rocks and are generally coarse gained (minerals grains greater than 1 millimeter in diameter), large, and often associated with mountain building. Mafic felsic, and intermediate intrusive rocks.

14. Anorthosite. It is the light-colored plutonic rock composed mostly of feldspar, labradorite, with very little pyroxene. The felsic plutonic rocks usually have quartz, large proportions of potassium feldspar, and lesser amounts of plagioclase and mafic minerals. On the other hand, intermediate and mafic rocks have increasingly larger proportions of dark iron-rich minerals.

Answer 2

Answer A:

Rhyolite has a lower density

Average density of Rhyolite is 2.5 g/cm³ whereas the average density of basalt is 3 g/cm³ So we can say that Rhyolite is less denser.

Answer B:

Rhoylite is more lighter

Rhyolite is either pink or grey whereas basalt is usually grey or black so we can say that Rhyolite has lighter color

Answer C:

Basalt is more melfic

Rhyolite is usually considered as felsic, while basalt is mafic. Generally felsic rocks make the bulk of the continental plates, while mafic basalt forms the seafloor.

Answer D:

Basalt has more amount of biotite

Basalt has 5% biotite in it whereas Thyloite has very rare amount of biotite in it so we can say that greater amount of biotite is present in Basalt

Answer E:

Quartz in Rhyolite may be present in amounts of 25% to 30%. whereas basalt has 20% - 60% quartz amount in it.

Answer 13:

Granodiorite is an example of felsic intrusive rock.

Answer 14:

Name of a very hard plutonic, igneous rock is Granite.