Volcanic plugs in the Atlin and Maitland areas consist of olivine nephelinite and basanite magmas. Limalok has erupted basaltic rocks, which have been classified as alkali basalts, basanite and nephelinite. These include nephelinite, basanite and peralkaline phonolite, trachyte and comendite lavas. If olivine is present, the rock may be classified as an olivine nephelinite. Tephritic nephelinite has a value between 0.6 and 0.9. Other rock types present include&colon; alkali basalt, nephelinite, lamprophyre, and carbonatite. The lava at Volcano Mountain is olivine nephelinite, which is an uncommon type of lava. The extinct volcano is 16 million years old and is formed of nephelinite. These include nephelinite, basanite and peralkaline phonolite, trachyte, and comendite lavas. Nephelinite has a value greater than 0.9. Melilite olivine nephelinite intrusives of Cretaceous age are found in the area around Uvalde, Texas. Nephelinite is exposed on the islands but is extremely rare. Nephelinite is yet richer in NaO plus KO compared to SiO. Nephelinite is an example of a silica-undersaturated igneous rock. Nephelinite is dark in color and may resemble basalt in hand specimen.