. Birds and nature . rthe stone acquires to pick up and holdbits of tissue paper, straws, etc. Some-times the friction from merely rubbingthe stone between the fingers will be suf-ficient to produce this electrical condi-tion, while many Brazilian Topazes, ifsimply pressed between the fingers, es-pecially in the direction of the prismaticaxis, become electric. The electricalcondition often persists from twenty-fourto thirty hours. The crystals of Topaz belong to theorthorhombic system of are usually elongated in the direc-tion of the prism and have sharp, brightfaces. They
. Birds and nature . rthe stone acquires to pick up and holdbits of tissue paper, straws, etc. Some-times the friction from merely rubbingthe stone between the fingers will be suf-ficient to produce this electrical condi-tion, while many Brazilian Topazes, ifsimply pressed between the fingers, es-pecially in the direction of the prismaticaxis, become electric. The electricalcondition often persists from twenty-fourto thirty hours. The crystals of Topaz belong to theorthorhombic system of are usually elongated in the direc-tion of the prism and have sharp, brightfaces. They vary much in size and of-ten are large. One crystal weighingtwenty-five pounds was found in Siberia. A well-marked characteristic of all To-paz crystals is their tendency to cleaveacross the prism parallel with its a cleavage plane can be seen cut-ting across the crystal shown in the up-per right-hand corner of the accompany-ing plate. This cleavage is so markedand the cleavage plane so bright and flat 216.
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