Pyroclastic rocks are the product of explosive volcanism. They are often felsic (high in silica). Pyroclastic rocks are often the result of volcanic debris, such as ash, bombs and tephra, and other volcanic ejecta.henocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye. Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix. Volcanic rocks often have a vesicular texture caused by voids left by volatiles trapped in the molten lava.
July 9, 2014. Frozen sperm must be stored in extremely cold temperatures (-196 F), but in order to ensure that the fewest possible sperm are damaged, the freezing must be gradual. Generally, the following procedure is followed:
You may want to consider freezing your sperm if: 1  you have a condition, or are facing medical treatment for a condition, that may affect your fertility. 2  you are about to have a vasectomy. 3  you have a low sperm count or the quality of your sperm is deteriorating.toring sperm is the only established way to preserve male fertility. Studies have shown that sperm can be retrieved and stored from patients as young as 13 years old, and storing sperm for a long time should not alter its ability to fertilise an egg.