. Annual report. New York State Museum; Science; Science. 158 NEW YORK STATE MUSEUM ahedron modifying the edges. Locally and at the time of pro- duction for many miles up and down the Delaware and Hudson Railway the crystals were known as " ; During visits to the mine the wr'ter made a careful study of hundreds and endeavored to detect other faces, freely using the reflecting gonio- meter in the measurements; but all the determinations led to such extraordinary indexes and to such variable results that the faces were believed to be merely interference planes produced by con-
. Annual report. New York State Museum; Science; Science. 158 NEW YORK STATE MUSEUM ahedron modifying the edges. Locally and at the time of pro- duction for many miles up and down the Delaware and Hudson Railway the crystals were known as " ; During visits to the mine the wr'ter made a careful study of hundreds and endeavored to detect other faces, freely using the reflecting gonio- meter in the measurements; but all the determinations led to such extraordinary indexes and to such variable results that the faces were believed to be merely interference planes produced by con- tact. The plane faces were found to be traversed by regular series of striations most of which follow the octahedral parting planes, but others are parallel to still other faces as described in the reference below to the writer's paper on " Gestreifte Magnetit- ; The finest of all the crystals of magnetite from Mineville is preserved in the office of Witherbee, Sherman & Co. at the mine and is about an inch in diameter. It is almost a mathematically perfect octahedron, having only one slight interference plane on one apex. Fortunately the matrix is also preserved but the crystal is believed to have come from the Old Bed (or Sanford) pit. All the pits are from time to time sources of cleavage pieces bounded by octahedral planes and often of large and regular size. The apparent cleavage is, however, really due to a series of parting. Fig. 34 Magnetite crystal from the Split Rock mine planes or gliding planes as is usually believed to be the case with minerals of the spinel group. Rarely these plates exhibit brilliant luster. In the coarse pegmatite of the "21 " pit, moderately large but very fragile crystals of magnetite are not uncommon, which are dodecahedral forms built up of octahedral triangular planes, a very common feature of Please note that these images are extracted from scanned page images that may have been digitally enha
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