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Collection: Directories and Documents > Pamphlets
Minerology Handbook by Eckert Mineral Research Prospector Supplies (PH 2-2) (28 pages)
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Page: of 28
C. Vitreous—A glassy luster. Examples: Quartz, Garnet, Fluorite.
D. Resinous—The luster of rosin, the substance used on violin bows
and in the prize fight ring. Examples: Sphalerite, Zinc Blende.
E. Greasy—Giving the appearance of a freshly oiled surface, Example:Milky Quartz.
F. Pearly—Having the luster of mother-of-pearl. Example: Talc.
G. Silky—The luster of satin or silk. Example: Asbestos, Fibrous
Calcite,
2. Color—Some minerals always occur in nature in the same color;
others range from one end of the rainbow to the other. Graphite, for
example, is always black; Sulphur is always yellow; Iron Pyrite is always brassy. Conversely, Quartz may be found colorless, yellow, purple,
brown, green, and other varieties. Tourmaline, having one of the widest color ranges, has been found colorless, red, blue, green, brown, black,
and in many other color combinations. The color of a mineral may be
attributed to the presence of impurities. Generally speaking, we may
say that minerals having a metallic luster do not vary much in color,
while those having an unmetallic luster may vary greatly.
3. Transparency—When we see with perfect clearness through a
mineral we say it is tramsparent. Examine: Rock Crystal, Quartz.
Opaque substances, on the other hand, do not permit the passage of
light, and consequently, we cannot see through them. See Argentite,
Galena. In between these extremes we have translucent substances,
which permit the passage of light but through which we cannot see
very distinctly. See Agate, Alabaster.
C. PROPERTIES DEPENDING UPON HEAT
Fusibility—When we speak of the fusibility of a mineral we mean
the ease with which it can be melted. Mercury, for example, melts at
all ordinary temperatures and is solid only at 40 degrees below zero or
lower. Stibnite melts in a match flame, which accounts for its use in
the manufacture of matches. Some minerals, like Graphite and Quartz
are infusible even in the hottest blowpipe flame.
For the purposes of comparison, fusibility may be expressed in terms
of the following scale:
1. Stibnite Easily fusible in match flame
2. Natrolite Fusible in candle flame
3. Almandite Garnet...........Fusible in blowpipe flame
4. Actinolite Fairly fusible
5. Orthoclase. Difficultly fusible
6. Calamine. Finest edge rounded in hot flame
7. Quartz Infusible
Two points should be kept in mind in connection with fusibilty.
First, the larger the specimen tested, the more difficult will it be to
fuse it. Second, if you are unable to fuse a mineral by holding it in
ye