Proceedings of the United States National Museum . Fig. 3.—Datolite. Similar to figure 2 BUT having some NEGATIVE PTEAMIDSNOT REPRESENTED BY CORRESPONDINGPOSITIVE FORMS Measurements of datolite, Figure 4 Form Symbol Quality description Measured Calculated No. Letter Gdt. MUIer * P « P 1 aAm 0 g rrizSu gQ& coO2co 00 co2 oy2 01 02 +Ji0 + k Vi +H1 +12 - 100• 210110120012Oil021104312122121 P. multiple o / 90 00 303030 57 5737 3722 0090 GO 58 0039 2720 00 0 / 0 2618 3133 0652 2690 0090 0090 0063 5621 4757 4254 05 90 00 28 14 07 38 18 21 33 90 00 57 52 38 33 21 39 o t 0 09 ?. Poor 17 26 3 Good
Proceedings of the United States National Museum . Fig. 3.—Datolite. Similar to figure 2 BUT having some NEGATIVE PTEAMIDSNOT REPRESENTED BY CORRESPONDINGPOSITIVE FORMS Measurements of datolite, Figure 4 Form Symbol Quality description Measured Calculated No. Letter Gdt. MUIer * P « P 1 aAm 0 g rrizSu gQ& coO2co 00 co2 oy2 01 02 +Ji0 + k Vi +H1 +12 - 100• 210110120012Oil021104312122121 P. multiple o / 90 00 303030 57 5737 3722 0090 GO 58 0039 2720 00 0 / 0 2618 3133 0652 2690 0090 0090 0063 5621 4757 4254 05 90 00 28 14 07 38 18 21 33 90 00 57 52 38 33 21 39 o t 0 09 ?. Poor 17 26 3 Good - 32 24 4 V. p . 51 45 5 Good 90 00 fi Med -- 90 00 7 Good 90 00 8 Med 63 31 q 21 41 in Poor -- 58 17 11 53 47 24 PROCEEDINGS OF THE NATIONAL MUSEUM VOL (50. In the several variations of the crystals above described the frontpinacoid a (100) is marked by vertical striations, which make thisform easy of identification and facilitate orientation of the crystals. The only other noteworthy featureis the presence of A (210), ordi-narily a rare form on datolite,which is present as narrow but dis-tinct faces on nearly every one oftlie larger crystals. The negativepyramid x^ (342) reported as anew form on datolite from West-field, Massachusetts, is present asa small face on one of the meas-ured crystals from Leesburg. Although all of the datolitecrystals of a large number of speci-mens from several veins had thegeneral habit above described, onespecimen, found loose on the eastside of the quarry, contained crys-tals of distinctly different specimen consists of brec-ciated limestone cemented by mas-sive datolite containing vugs linedwith colorless transparent crystalsup to 6 millimeters in diameter,all of which have the developmentshown i
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Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
