Non-silicates constitute less than 10% of the Earth's crust. The most common non-silicates are the carbonates, the oxides, and the sulfides. There are also naturally occuring phosphates and salts. There are a few elements which occur in pure form, including gold, silver, copper, bismuth, arsenic, lead and tellurium.Carbon is found in both graphite and diamond form.he most common minerals are the silicates, as one would guess by looking at the abundances of the elements in the Earth's crust, but there is a great variety of minerals. Minerals are classified in many ways, including hardness, optical properties, crystal structure, etc.
Vas deferens: The tube that connects the testes with the urethra. The vas deferens is a coiled duct that conveys sperm from the epididymis to the ejaculatory duct and the urethra.
Vasa praevia (vasa previa AE) is an obstetric complication in which fetal blood vessels cross or run near the external orifice of the uterus. These vessels are at risk of rupture when the supporting membranes rupture, as they are unsupported by the umbilical cord or placental tissue.asa previa is present when fetal vessels traverse the fetal membranes over the internal cervical os. These vessels may be from either a velamentous insertion of the umbilical cord or may be joining an accessory (succenturiate) placental lobe to the main disk of the placenta.