The beryl possesses the same crystalline form and specific gravity as the emerald, but its hardness, especially in the blue and white varieties, is sometimes greater. They are both silicates of alumina, and the only perceptible difference in the two stones is in the color. Cleaveland thought that as the emerald and beryl had the same essential characters, they might gradually pass into each other; and Klaproth, finding the oxides of both chrome and iron in one specimen, was led to take the same view. The crystals of true emerald are almost always small, with the exception of those found in the Wald district in Siberia, whilst those of the beryl vary from a few grains to more than a ton in weight. The crystals of both are almost invariably regular hexahedral prisms, sometimes slightly modified. Those of the beryl we sometimes find quite flat, as though they had been compressed by force; then again they are acicular and of extraordinary length, considering their slender diameter. Sometimes their lateral faces are longitudinally striated, and as deeply as the tourmaline, so that the edges of the prism are rendered indistinct. Other crystals are curved, and some perforated in the axis like the tourmaline, so as to contain other minerals. Sometimes they are articulated like the pillars of basalt, and separated at some distance by the intervening quartz. These modified forms give rise to curious speculations as to their formation and origin. If we admit the action of fire (which is improbable), then the separation may be easily explained; but if we insist that they were deposited in the wet way and by slow process, how can we account for the dislocation? “By electricity,” whispers a friend,--“by telluric magnetism, that wonderful unexplained and mysterious force which has caused the grand geological changes of the globe, and is still at work.” Sometimes the crystals of beryl are of two distinct colors, but generally they are of one color, often shading into white at either extremity. They may exhibit the richest golden-yellow, or a light cerulean blue, or a clear sea-green like those described by Pliny, now called aqua-marines. “Qui viridatem puri maris imitantur.” One distinction between beryl and quartz is afforded by the appearance of its fracture. A crystal of beryl breaks into smooth planes, the faces of which are at right angles to the axis of the prism; while the fracture of the surface of broken quartz is invariably conchoidal. Blue beryls were highly prized by the ancients. Beautiful specimens are found in the glens of the Mourne Mountains in Ireland. But finer gems are brought from the granite district of Nertschinsk, in Siberia, and also from various localities in the Uralian and Altaian Mountains, where the Romans were supposed to have obtained them in early times.