|
.
Axinite Mineral Facts:
Chemical Formula: Ca7Al4B2(SIO4)8
The chemical make up also includes varying amounts of ferrous
iron, manganese, magnesium and hydrogen isomorphous with the calcium,
and ferric iron with the aluminum.
Colors:
Various shades, brown to gray,
light green, yellows, etc.
Hardness:
6.5 to 7.0
Density:
3.27 to 3.35
The density
is typical
for a nonmetallic mineral.
Cleavage:
Distinct, parallel to the brachypinacoid.
Crystallography:
Triclinic
Crystals usually thin with sharp edges (hence the name) but varied in
habit.
Luster:.
Vitreous
luster.
Transparent to opaque.
Optics:
(Refractive Index): a= 1.6720; b= 1.6779; y = 1.6810
|
|
|
Composition,
Structure and Associated Minerals:
Fusible at 2.5-3 with intumescence. When mixed with potassium bisulphate
and fluorite and the mixture heated
on platinum wire gives a green flame (a test for presence of boron).
Not acted
on by acids unless previously heated, when it
gelatinizes. After fusion, however, it dissolves readily with the production
of gelatinous silica. The mineral is easily characterized by its
crystallization and the green color it imparts to the flame. It has not been
produced artificially. Pseudormorphs of chlorite after axinite have been
found in Dartmoor, England..
Identification and Diagnostics
Axinite is
especially noteworthy for its richness in crystal forms.
The mineral is a complicated borosilicate for which the formula given
above is merely suggestive. Analyses of crystals from different localities
vary so widely that no satisfactory simple formula has been proposed for the
mineral.
Occurrence,
Localities and Origins:
Axinite makes for attractive
mineral specimens, and is collected as such. On rare occasions, it is cut
and used as a gem
stone. The name is derived from a Greek word meaning ax, in allusion
to the wedgelike shape of the crystals. Axinite crystals occur in cracks in
old siliceous rocks. It is found also in ore veins and as a component of a
contact rock composed mainly of augite, hornblende and
quartz, occurring
near the peripheries of granite and diabase (dolerite) masses. It was formed
by the aid of pneumatolytic processes.
Localities for Axinite:
Excellent crystals of axinite are found at Andreasberg and other places in
the Harz Mts. ; near Striegau, in Silesia; near Poloma, in Hungary; at the
Piz Valatscha, in Switzerland; near Vernis and at other points in Dauphine,
France; at Botallak, St. Just, Cornwall, England; Obira, Japan; at
Konigsberg, Norway; Nordmark, Sweden; Lake Onega, and Miask, Russia; at
Wales in Maine Franklin Furnace, New Jersey,and at South Bethlehem, Penn.
Return to the
Mineral Collectors Information Page
|
