PHORMION, Athenian admiral in the 5th century B.C., was the son of Asopius, of the deme Paeania. He first appears in 44o B.C. when he was sent with reinforcements to the Athenian troops Mos, stone). The term "clinkstone" was formerly given by geol ogists to many fine-grained compact lavas, which split into thin tough plates, and gave out a ringing sound when struck with the hammer. Some of these were phonolites in the modern sense, but as the name clinkstone was used for a large variety of rocks, many of which have no close affinities with one another, it has been discarded and "phonolite" substituted. The group includes rocks which are rich in alkalis with only a moderate percentage of silica ; hence they contain no free quartz but much alkali-felspar (sanidine and anorthoclase) and nepheline. Large plates of sani dine are often visible in the rocks ; the nepheline is usually not obvious to the unaided eye. Most phonolites show fluxion struc ture, both in the orientation of their phenocrysts and in the smaller crystals which make up the ground-mass ; and this de termines to a large extent the platy jointing. Although vitreous and pumiceous forms are known they are rare, and in the great majority of cases these rocks are finely crystalline with a dull or shimmering lustre in the ground-mass.
Dominant Minerals.—These are sanidine, nepheline, pyrox ene, amphibole, various felspathoids and iron oxides. The sani dine is usually in two generations, the first consisting of large crystals of flattened and tabular shape, while the second is repre sented by small rectangular prisms arranged in parallel streams in the ground-mass ; these felspars are nearly always simply twinned on the Carlsbad plan. They contain often as much soda
as potash. The nepheline takes the form of hexagonal prisms with flat ends, and may be completely replaced by fibrous zeolites, so that it can only be recognized by the outlines of its pseudo morphs. In some phonolites it is exceedingly abundant in the ground-mass, and these rocks form transitions to the nephelinites (nephelinitoid phonolites) ; in others it is scarce and the rocks resemble trachytes containing a little nepheline (trachytoid pho nolites). The felspathoid minerals, sodalite, hailyne and nosean, which crystallize in isometric dodecahedra, are very frequent components of the phonolites; their crystals are often corroded.
before Samos. In 432 he took out reinforcements to the force blockading Potidaea, took over the command from Callias, and completed the circumvallation of the city. He seems to have stayed in the north-east, as in 431 he was co-operating with Per diccas against the Chalcidians. In 43o he was sent with 3o ships to help the Acarnanians against the Ambraciots. That winter there followed the operations on which his fame is based. He was given 20 ships and stationed at Naupactus, to effect a blockade of Corinth from that side. In the summer of 429 a superior Peloponnesian fleet arrived, and was decisively beaten by Phor mion. In a second engagement he was forced to retreat, but turned and again routed his pursuers. He was probably dead by 428.