 | James Dwight Dana - 1878 - 502 Seiten
...these there are gradual transitions to the pellucid quartz crystal that looks like the best of glass. Sandstones and freestones are often wholly quartz,...probable that this mineral will be often encountered in mincralogical rambles. Let the first trial of specimens obtained be made with a file, or the point... | |
 | James Dwight Dana - 1884 - 502 Seiten
...these there are gradual transitions to the pellucid quartz crystal that looks like the best of glass. Sandstones and freestones are often wholly quartz,...obtained be made with a file, or the point of a knife, or some.other means of trying the hardness ; if the file makes no impression, there is reason to suspect... | |
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... and of various degrees of glassy lustre to a dull stone without the slightest glistening. The common grayish cobble-stones of the fields are usually quartz, and others are dull red and brown ; from these there are gradual transitions to the pellucid... 