False. Large crystals typically form from slow cooling of a solution, which allows molecules to arrange themselves into a well-defined crystal structure. Rapid cooling tends to produce smaller crystals or even amorphous solids, as the molecules do not have enough time to organize properly.
Large, well formed crystals form in solutions that cool rapidly. When solutions cool slowly, crystals are more likely to nucleate in higher numbers at the same time, leading to many very small and irregular shaped crystals.
Orthoclase feldspar is commonly found in association with large muscovite crystals. This mineral combination is often seen in pegmatite deposits, where slow cooling allows for the growth of large crystals.
They grow large.
Crystal size in these rock types is determined by their rate of cooling. Pegmatites have large crystals due to very slow cooling. Obsidian has microscopic crystals due to almost instantaneous cooling.
Large crystals in igneous rocks usually form when the magma cools slowly underground, allowing the crystals more time to grow. The composition of the magma, the cooling rate, and the amount of available space for crystal growth all play a role in determining the size of crystals in the rock. Rapid cooling at the Earth's surface typically results in the formation of fine-grained rocks.
Basalt crystals are typically small to microscopic in size due to the rapid cooling of lava, which results in limited time for crystal growth. This rapid cooling process usually prevents the development of large crystals in basalts.
large crystals
A rock with large crystals scattered on a background of much smaller crystals is called a porphyry. This rock texture is the result of two stages of cooling, where large crystals formed during the slower cooling stage, followed by smaller crystals forming during rapid cooling.
Large, well formed crystals form in solutions that cool rapidly. When solutions cool slowly, crystals are more likely to nucleate in higher numbers at the same time, leading to many very small and irregular shaped crystals.
a porphyritic rock. This texture indicates that the rock underwent two stages of cooling: slow cooling deep underground (resulting in the large crystals) followed by faster cooling near the surface (resulting in the small crystals).
The resulting texture is porphyritic. The slower cooling stage allows large crystals to form (phenocrysts), while the faster cooling stage results in the formation of smaller crystals in the remaining magma (groundmass). This gives the rock a mixture of large and small crystals, creating a porphyritic texture.
Igneous rocks with large crystals are called intrusive rocks, formed from magma cooling slowly beneath the Earth's surface, allowing for large crystals to form. Igneous rocks with small crystals are called extrusive rocks, formed from lava cooling quickly on the Earth's surface, resulting in small crystals due to rapid cooling.
Orthoclase feldspar is commonly found in association with large muscovite crystals. This mineral combination is often seen in pegmatite deposits, where slow cooling allows for the growth of large crystals.
Slower rates of cooling will create larger crystals. Rapid cooling allows little time for element accumulation in the crystal, therefore, the crystals created will be smaller. Larger, visible crystals in igneous rock indicate that the magma was slow cooling, usually at depth. Much smaller crystals in igneous rock indicate rapid cooling of lava, usually at or near the surface. Crystals in igneous rock will grow larger and have more time to accumulate material for their growth the more time they have at their crystallization temperature.
They grow large.
Crystal size in these rock types is determined by their rate of cooling. Pegmatites have large crystals due to very slow cooling. Obsidian has microscopic crystals due to almost instantaneous cooling.
Large crystals in igneous rocks usually form when the magma cools slowly underground, allowing the crystals more time to grow. The composition of the magma, the cooling rate, and the amount of available space for crystal growth all play a role in determining the size of crystals in the rock. Rapid cooling at the Earth's surface typically results in the formation of fine-grained rocks.