Chap. VI. ] 
SPESSARTITE. 
175 
Very frequently the mineral breaks so as to show a zoned surface. 
^ This is found to be, not a true fracture, but usually the 
°' surface of contact with another crystal, the two 
having mutually stopped each other's growth at the surfaces where they 
meet. These zoned surfaces are also often found at the contact of 
an imperfectly developed crystal with the quartz in which it is found. 
It is only with difficulty that this zoning can be obtained on a true 
fracture surface. When it is carefully examined it is seen to be due 
to a layered structure of the garnet parallel to the faces of the 
trapezohedron. This seems at first sight surprising because the 
striations so often seen on the faces of the trapezohedron, make it look 
as if the mineral were composed of lamellae parallel to the faces of 
dodecahedron, d. 
The case noted on page 174 of a crystal with its trapezohedral faces 
^. composed each of two vicinal hexoctahedral faces 
suggests, however, that the striations often observed 
on the trapezohedral faces of the Indian spessartites may really indi- 
cate an oscillatory combination with the hexoctahedron rather than 
with the dodecahedron. The striations are parallel both to certain of 
the edges of the hexoctahedron and to all the faces of the dodecahe- 
dron. The hexoctahedral interpretation agrees with the zoning. 
I have not particularly tested the hardness of the mineral ; but it 
seems to agree with the values given in the text- 
bpecific gravity. , . ° ... 
books. Ihe specific gravity of spessartite is given 
as 4:'0 to 4"3 and I find that the few I have tested lie within these limits, 
tending to be from 4-15 to 4-25. The following show the actual values 
that have been determined for Indian spessartites : — 
Bichua 402. 
Chargaon (figured) .... 4-16. 
Kulu 411 and 416. 
This mineral exhibits considerable variety of colour. It is not 
^^j^^ very often that the crystals are perfectly trans- 
parent and free from darkening due to alteration ; 
but when the crystals are in this condition they are often of a most 
beautiful bright orange colour, and if they could be obtained in 
quantity and of a fair size they might be used as a most 
lovely gem. Frequently the colour is considerably darker than this, 
being then usually orange-red, the tint of which is often exactly the 
same as that of ordinary guava jelly. More rarely the colour is even 
