Igneous Rock

Perlite is an igneous, and perlite is an amorphous volcanic glass and is created from a mixture of hydrated obsidian and mass amounts of water.

Your question as phrased is unclear. I will proceed to answer both interpretations I have of your question. Note: When magma crystallizes, it forms igneous rocks.

1) What is the change of state when magma forms from igneous rock? - Melting. Rocks are the solid state of matter and magma is the liquid state (although it can be a very viscous liquid). Changing something from solid to liquid is melting.

2) What is the change of state when magma crystallizes to form igneous rocks? - Solidification/Freezing. Magma becomes too cold to continue in a liquid state, it solidifies and crystallizes into solid igneous rocks: freezing.

The rock melts, just like most other solids do when heated. Magma is to rock as water is to ice.

heterogeneous mixture

It acts as an abrasive.

That would depend on what the cementing material is and how densely it is compacted.

Molten rock (igneous rock) may be worn down (weather and erosion), turning into pebbles, then due to things such as floods, they can get washed down into a lake where the water is calm. Things such as clay and sand settle down too, as well as other rocks. Over many years (we're talking thousands, millions of years here) all of those things get compressed and eventually the pressure is so great that it forms one big bit of rock. That's why in sedimentary rock you see all the layers, they are all the layers of things like sand, clay and rocks all pressed together. I think that's how a lot of sedimentary rocks are made. Metamorphic rock may also be turned into sedimentary this way.

All rocks can become igneous rocks.

With weathering and erosion, an igneous rock can become a sediment. Then with compaction and cementation, it can become a sedimentary rock. With heat and pressure, it will turn into a metamorphic rock. Or it can melt and turn into an igneous rock.

There are many more ways rocks can change types... that is the rock cycle.

Not necessarily. Intrusive igneous rocks, especially pegmatites, can have large crystals.

Melt and recrystallize

Igneous rocks, which come in many different forms.

Never say never, but it's mica.

Igneous rock typically begins as magma, which is molten rock located beneath Earth's surface. This magma can solidify underground to form intrusive igneous rock or erupt onto the surface as lava and cool to form extrusive igneous rock.

Melting and solidification are the processes that must occur for a rock to change into igneous rock.

volcanic because it is an intrusive rock

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its false

A Sill is formed

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igneous rock

because most intrusive igneous rock are found underground and diorite is found under the earth.

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No, coal is not an igneous rock at all. Coal is made from sedimentary rock that is squeezed under the ground by great pressure.