Triclinic Section – BeryI Composition, Crystallization & Structure

The only member of the Tridinic Section of the Amphibole Group is the rare mineral renigmatite, Na₄Fe₉AIFe”’(Si,Ti)₁₂O₃₈.

BeryI
Composition. Be₃.A1₂ Si₆O₁₈. Analyses show a small amount of water. Small amounts of the alkali oxides, often in part consisting of crosium oxide, frequently replace the beryllium oxide.

Crystallization. Hexagonal. Strong prismatic habit. Frequently vertically striated and grooved. Forms usually present consist only of prism of first order and base. Small pyramid faces of both the first and second orders sometimes occur, but the pyramid faces are rarely prominent. Dihexagonal forms quite rare. Crystals frequently of considerable size with rough faces.

Structure. In crystals. Also massive, with indistinct columnar structure or granular.

Physical Properties. H. = 7.5-8. G. = 2.75-2.8. Vitreous luster. Color commonly bluish green or light yellow; may be deep emended-green, golden-yellow, pink, white or colorless. Transparent to sub translucent. Frequently the larger, coarser crystals Blow a mottled appearance due to the alternation of clear transparent spots with cloudy, almost opaque portions.

Tests. B. B. whitens and fuses with difficulty at 5-5.5 to an enamel. Yields a little water on intense ignition. Insoluble in acids. Recognized usually by its hexagonal crystals, its hardness, color, etc.

Varieties

• Ordinarily Beryl. In coarse translucent to opaque crystals ar masses, usually of a pale greenish blue or yellow color. Sometimes in very large crystals; one from Grafton, New Hampshire, measured over 4 fect in length with a diameter between 20 and 30 inches, weight 2900 pounds.
• Aquamarine. Name given to the pale greenish blue transparent
• stone. Used as a gem.
• Golden Beryl. A deep golden-yellow variety, which, when clear,
• is used as a gem.
• Rose Beryl. A variety varying in color from pale pink to deep rase. Beautiful gem material from Madagascar has been name morganite.
• Emerald. The true emerald is the deep green transparent beryl and is among the most highly prized oil gems. The color is due small amounts of chromium.

Occurrence. Beryl, although containing the rare element beryllium, is a rather common and widely distributed mineral. It occurs usually in granite rocks, either in druses or in pegmatite veins. It is also found in mica-schist and in connection with tin ore: Emeralds oil gem quality occur in a dark bituminous limestone at Muse, 75 miles northwest of Bogota, Colombia. This locality has been worked almost continually since the middle of the sixteenth century, and has furnished the greater part of the emeralds oil the world. Another famous locality for emeralds is in Siberia on the river Takowaja, 45 miles east of Ekaterinburg. They occur in a mica-sehist associated with phenacite, chrysoberyl, rutile, ete. Rather pale emeralds have been found in small amount from Alexander County, North Carolina, associated with the green variety of spodumene, hiddenites. Beryl of the lighter aquamarine color is much more common, and is found in gem quality in Brazil, Siberia, and many other localities. From the pegmatites of Madagascar. In the United States they have been found in various places in Maine, New Hampshire, Massachusetts, Connecticut, North Carolina, Colorado, ete. The golden beryl has been found in Maine, Connecticut, North Carolina and Pennsylvania; also in Siberia. And Ceylon. The rose-colored beryl has been found in San Diego County, California, associated with pink tourmaline and the pink spodumene, kunzite. A similar occurrence in Madagascar has furnished magnificent rose-colored stones (morganite).

Use. Used as a gem stone of various colors. The emerald ranks as one of the most valuable of stones, at times being of much greater value than the diamond.

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