Question

question 3 (2 points)
listen
obsidian cools so rapidly that no gas bubbles can form inside of it. its texture is referred to as
vesicular
porphyritic
glassy
fragmented
question 4 (2 points)
listen
the first mineral to melt from a rock is
olivine
gold
silver
quartz

Explanation:

• Question 3: Obsidian is an igneous rock that forms from rapidly cooling lava. When lava cools very quickly, there is no time for mineral crystals to grow. Instead, it forms a natural glass. Vesicular texture has gas bubbles (vesicles), porphyritic has large crystals in a finer - grained matrix, and fragmented is related to broken - up rock material. Since obsidian has no gas bubbles and is glass - like, the texture is glassy.
• Question 4: Quartz has a relatively low melting point compared to olivine (which has a high melting point and is one of the last to melt in some rock - melting scenarios). Gold and silver are not common minerals in most rocks in the context of rock - melting (they are usually in trace amounts or in specific ore deposits). When a rock starts to melt, minerals with lower melting points melt first. Quartz has a lower melting point than olivine in many rock - forming mineral assemblages.

Answer:

• Question 3: glassy
• Question 4: quartz