In many basic igneous rocks, such as gabbro and dolerite, scapolite replaces felspar by a secondary or metasomatic process. Some Norwegian scapolite-gabbros (or diorites) examined micro scopically furnish examples of every stage of the process. The chemical changes involved are really small, one of the most im portant being the assumption of a small amount of chlorine in the new molecule. Often the scapolite is seen spreading through the felspar, portions being completely replaced, while others are still fresh and unaltered. The felspar does not weather, but re mains fresh, and the transformation resembles metamorphism rather than weathering. It is not a superficial process, but appar ently takes place at some depth under pressure, and probably through the operation of solutions or vapours containing chlorides. The basic soda-lime felspars (labradorite to anorthite) are those which undergo this type of alteration. Many instances of scapoliti zation have been described from the ophites (dolerites) of the Pyrenees. In the unaltered state these are ophitic and consist of pyroxene enclosing lath-shaped plagioclase felspars; the pyroxene is often changed to uralite. When the felspar is replaced by scapo lite the new mineral is iresn anci grains of hornblende. Extensive recrystallization often goes on, and the ultimate product is a spotted rock with white rounded patches of scapolite surrounded by granular aggregates of clear green hornblende: in fact the original structure disappears.
3. In Norway scapolite-hornblende rocks have long been known at Oedegarden and other localities. They have been called spotted gabbros, but usually do not contain felspar, the white spots being entirely scapolite while the dark matrix enveloping them is an aggregate of green or brownish hornblende. In many features they bear a close resemblance to the scapolitized ophites of the Pyrenees. It has been suggested that the conversion of their original felspar (for there can be no doubt that they were once gabbros, consisting of plagioclase and pyroxene) into scapolite is due to the percolation of chloride solutions along lines of weak ness, or planes of solubility, filling cavities etched in the substance of the mineral. Subsequently the chlorides were absorbed, and pari passu the felspar was transformed into scapolite. But it is found that in these gabbros there are veins of a chlorine-bearing apatite, which must have been deposited by gases or fluids ascend ing from below. This suggests that a pneumatolytic process has been at work, similar to that by which, around intrusions of granite, veins rich in tourmaline have been laid down, and the sur rounding rocks at the same time permeated by that mineral. In the composition of the active gases a striking difference is shown, for those which emanate from the granites are mainly fluorine and boron, while those which come from the gabbro are principally chlorine and phosphorus. In one case the felspar is replaced by quartz and white mica (in greisen) or quartz and tourmaline (in schorl rocks) ; in the other case scapolite is the principal new pro duct. The analogy is a very close one, and this theory receives much support from the fact that in Canada (at various places in Ottawa and Ontario) there are numerous valuable apatite vein deposits. They lie in basic rocks such as gabbro and pyroxenite, and these in the neighbourhood of the veins have been extensively scapolitized, like the spotted gabbros of Norway.
4. In many parts of the world metamorphic rocks of gneissose character occur containing scapolite as an essential constituent. Their origin is often obscure, but it is probable that they are of two kinds. One series is essentially igneous (orthogneisses) ; usually they contain pale green pyroxene, a variable amount of felspar, sphene, iron oxides. Quartz, rutile, green hornblende and
biotite are often present, while garnet occurs sometimes ; hyper sthene is rare. They occur along with other types of pyroxene gneiss, hornblende gneiss, amphibolites, etc. In many of them there is no reason to doubt that the scapolite is a primary mineral. Other scapolite gneisses equally metamorphic in aspect and struc ture appear to be sedimentary rocks. Many of them contain cal cite or are very rich in calc-silicates (wollastonite, diopside, etc.), which suggests that they were originally impure limestones. The frequent association of this type with graphitic-schists and andalu site-schists makes this correlation in every way probable.
S. F.) SCARAB (Lat. scarabaeus, connected with Gr. KapOos), literally a beetle, and derivatively an Egyptian symbol in the form of a beetle. The Egyptian hieroglyph pictures a dung beetle (Scarabaeus sacer), which lays its egg in a ball of dung, and may be seen on sandy slopes in hot sunshine compacting the pellet by pushing it backward uphill with its hind legs and allow ing it to roll down again, eventually reaching a place of deposit. Whatever the Egyptians may have understood by its actions, they compared its pellet to the globe of the sun. The beetle is common on both shores of the Mediterranean ; the Egyptian name was klieperer, kheperi, and the sign spelt the verb kh5pi(r) mean ing "become" and perhaps "create," also the substantive "phenomenon" or "marvel." The insect was sacred to the sun god in his form kheperi at Heliopolis, and has been found mummi fied. A colossal scarabaeus of granite in the British Museum probably came from the temple of Heliopolis. The scarabaeus was much used in Egyptian religions, appearing sometimes with outstretched wings or with a ram's head and horns as the vivifying soul. It is often seen in this guise on coffins of the New Kingdom and later, when it also became the custom to place in the bandages of the mummy a large stone scarab engraved with a chapter of the Book of the Dead. This chapter, the 64th, identified the object with the heart of the deceased and conjured it not to betray him in the judgment before Osiris. A winged scarab might also be laid on the breast; and later a number of scarabs were placed about the body. These are often of hard stone and of fine workmanship. Another and even more important class of Egyptian antiquities is in the form of scarabs, pierced longitudinally for a swivel or for threading, and having the bases flat and engraved with de signs. These were intended principally for seals, but might also be used as beads or ornaments. They are thus found, engraved or plain, strung on necklaces, and amethyst scarabs with plain bases are common articles of Middle Kingdom jewellery. But the em ployment of scarabs as seals is proved by the impressions found on sealed documents of the Middle and New Kingdom, on several occasions the impressed clay seals alone have been found hardened and preserved by the fire which had destroyed the archives them selves. The seal type of scarabaei is extremely abundant, and the designs engraved beneath them show endless variety. Some have inscriptions carefully executed, but frequently corrupted by illiter ate copying until they became meaningless. The inscriptions are sometimes "mottoes" having reference to places, deities, etc., or containing words of good omen or friendly wishes, e.g., "Memphis is mighty for ever," "Ammon protecteth," "Milt give thee long life," "Bubastis grant a good New Year," "May thy name endure and a son be born thee." Such are of the New Kingdom or later. Names and titles of officials appear, most commonly in the Middle Kingdom.