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t 901.

137
the crystals are oflen terminated in a number of points; occasionally these end portions have an asbestos -like appearance.
Also bere .and there ou tbe longitudinal faces of the crystals
considerable depression!' have been formed by corrosion; thesedepressions are lined with needles and splinters like thoseoccurring at the ends of the crystals. Between tbese fibres
of aegirine and onen oriented parallel to them occur lorenzenite crystals of type H. Elpidite crystals also occur in alike manner, and It is evident that the two minerals have formed
simultaneously and during the decomposition process of theaegirine. On the new-formed minerals tbere occur small curved
scales and basin - sbaped crystal tables of polylithionite as thelatest formation. Also on small fresh aegirine crystals one finds
lorenzenite crystals in such a position that the two minerals havetheir vertical axes parallel, while the first pinacoid of the former
mineral coincides with the second pinacoid of the latter.
The later generation of aegirine consists of small green
translucent brilliant needles, the terminations of which arealso brilliant. Associated with this aegirine occur most of
the lorenzenite crystals of type 1. The very brilliant needleshaped crystals of this type generally occur implanted inirregular orientation on feldspar, wbere that mineral borders on
primary aegirine. Small secondary crystals of microcline, albite,and epididymite are the usual companions of this type of lorenzenite. These minerals are generally surrounded by a dark, earthy
substance, which is intensely soiling and probably owes its
origin to the decomposition· of rbodochrosite, of which remains
are sometimes visible.

28. Leucosphenite.
Tbe name ilf tbis new mineral is derived from the Greekwords A'/}%O" white,· and arpil'tI, a wedge, and chosen in allusion
to the white colour of the mineral and the wedge-like form of
the crystals.

138
The mineral has been found in but small quantity and oofy
in the crystalline stale.

The crystals seldom attain more thana'" in length and 1-2'" in breadth and thickness; the majority are considerably smaller in size. They belong to the monoclinic system nnd are fairly regularly developed, so that fairly
accurate measurements could be obtained. The cry~tallographicalconstants are derived from the following angular values:(130):(130) =120°,15', (130):(001) -= 88° 19', and(101): (001) =53° 21'.

The axial ratios calr.ulated from them area : b : c = 0,6813: I : 0,8601.
p == 93° 23'.
According to these constants the forms present ha\'e thefollowing symbols:

a -= {lOO}, b ={OIO}, c =- {OOI}, z .... LOll}, d = {IOI},
m = {110}, n = {130}, 8 == {112}, P = {fll},g = {133}, r = {263}.

Nearly all the crystals of this mineral that I have observedare very like one another with regard 10 their habit.

Only 8S

regards the presence or absence of certain subordinate forms
do they present any variation.

The forms that are always pre-sent and give the crystals their constant habit, are c, band PI.
The crystals are always elongated in the direction of the a-axis
into rectangular prisms, bonnded in the longitudinal zone by
the second and third pinacoids.

The crystals are always ter-minated by the form n, the faces of which form the wedgelike ends that characterize the leucosphenite crystals (Fig. 4,Plate VIII.

The faces of the third pioacoid are generally pre-dominant, so that the crystals are more or less tabular parallelto them.

Howe\'er there occur individuals on which the saidpinacoids are almost equally developed (Fig. 9, Plate VIII or139

which are tabular parallel to the second pinacoid. The combination-edges between the pinacoids in the longitudinal zone
ure sometimes truncated by the prism of the first order x,
whose faces are always narrow (Figs. 5, 9, Plate VIII. The prism(pinacoidl of the second order d occurs distinclly de\'eloped only
on a small number of crystals (Figs. 5, 7, 8, 9, Plate VlIl. Its
faces are almost always smooth and brilliant. Occasionally they
are tolerably large. The prism of the third order m occurs,or is at least present as traces on every crystal of leucosphenite; its faces are, hOll"ever, in most cases very small andOften they occur only as step-likeindistinct (Figs. -4 - 61.
formations on the edge between nand d. The prism of thefourth order p is a form of tolerably common occurrence, Rnd
its faces are occasionally rather large. In the majority ofcases, however, they are small (Fig. 6) and uneven with nohigh lustre. The two forms 9 and r occur as extremely narrow truncations on the obtuse combination - edge between nand c (Figs. 6, 7). Onen the two forms occur together. The
faces are brilliant, but their edges are frequently irregularlyrounded off.
The forms a and 8 have been observed only on a single
crystal. This crystal, which measures a little more than 1alIain length and 1!lI a"a in thickness, is represented by Fig. 9. It
was found associated with minerals quite different to thosewhich generally accompany leucospheniLe, and it also differsin habit from other crystals of this mineral. Like them itis prismatically elongated in the direction of the a-axis andbounded in tbe zone of tbis axis by the secoud and the third
pinacoids, which are almost equally well developed. Their combination-edges are truncated by narrow fares belonging to theform x. The cry!\tal is developed only at one end and is therecolourless and perfectly clear. The other end, by which thecrystal has been attached, is opaque. As on tbis crystal theprismatic form n is very subordinate, the wedge-lik.e termination

110that otherwise characterizes the mineral is not found on thisindividual. On the other hand, the form m has on this crystal
attained a development to which nothing corresponding is foundon the common leucosphenite crystals. The faces of the form
p are large, smooth and of a magnificent lustre. The pinacoidof the second order d is represented by a very small, but brilliant
and quite determinable face. The face a of the first pinacoidis large, smooth and brilliant. The largest of ~he terminal
planes of this crystal, however, are those of the form 8. They
belong to the zones [001, 110) and 1011, JOJ). which is sufficient
for a cerlain determination of the form.
The leucosphenile crystals of the common type are generally
developed on both ends. The faces of the third pinacoid are,as a rule, striated longitudinally, which striation is due to thealternation of faces belonging to the forms c and z. Sometimes the striation disappears, at least in places, and thenthe face is dull. Some crystals are striated on one side Ind
dull on the other. When dull and striated spots occur on thesame faces, they border irregularly on one another. The facesof the second pinacoid are also striated, but on them the striation runs in the vertical direction, consequently across theirlongitudinal direction. Here it is the form n which causes
the striation by alternation. In most cases the striation is mostmarked at the ends of the faces; the middle portions of thefaces generally have no striation. These faces are, besides,
seldom quite plane, but either show a continuous rounding oran abrupt bending, owing to which their ends make a smaller
angle with n than the unbroken plane would make. The difference I have found almost unvariably to be about 10 towards
each end. Also on the faces of the form n occurs a verticalstriation, which, however, does not essentially interfere with tbe
measurement of the angles. The crystals are not in generalvery sharply developed, their edges and corners usually being
somewhat rounded off. Only the crystal represented by Fig. 9,

141Plate VII, forms an exception from this rule, being perfectlydeveloped in every respect.
In the annexed table are given the measurements obtainedfor eight crystals, together with the corresponding calculated
values.
Q,

I:::I"".., '"

as ca<;,;l-rCla:Co
OC0t-~

00

co:'"
001>'
0~0";;,

0Cl

Cl"ClcortiQ)

tlD.,.

I::

....
..ccc
Eo-"a:OC.,.,-.,.
. ""
Cl""

e0or.
er.

0Q)

...

Co...

0rCl- ..

00IN;.

Cl00""MINiN:..

"ClIN

e-oMco;r"INccClcoM0'"

~M;;,

..
IN0M

000

~00:.,.

00~.,'"00coIN..
j:.

....;;".

e-"00'"Cl....r"

1>'

CoIN'"oS

Co

CoIN""

Cl-0

M

r-"cocoCl

IN0oS

IN-IN

ClCc

IN00'"
coco'" ....
Cl.,.Co
0:>00M

or.

OC'"

.,.

:"

000
M

0.,.:.. .,. :..
""co "Clco'"'"

:..
.,.
0QC

cc

cc00'"""

Ooa:

M0.Q

00M;;,

M0M0~.,.

.,.Cc~

IN0t-000Co.,.

0._---a:

M0c:

M'"

IN00OC0Co.,....,j:.

""0M.,.
'" .... '"0.,.00 .,.Co....,.""
"'"
co '"
Cl--_.- -M
0Cl... a. ...
-. ...
.....,.
" ..
""r- :..
IN0.,.
M,.,,:!

r- ------ --------... :.,.Of' a.
j:.

0Cl0

"" '" ""'"
Cl--

r-00~

CO00

- oS ~ -0 -0 -0 £ ~ 8 ~- ~-8 -::::.
..s- - - - - - '"""
8ClClIM1-MCl-0M-0-0-0MMM

M1--""""

142
Twinning is tolerably common in leucosphenite. The law
according to which the twins are formed is as follows: thetwinning plane is the third pinacoid c {00l}; thetwinning axis is a normal to this; one of the individuals is revolved 180° about the twinning axi~
As the salient and re-entering angles between the faces of theform n on the sub-individuals deviate very little from

J SOo,

these twins ar,e not easily distinguished from simple crvstals
IFig. 8, Plate VII}.

The vertical axes of the two sub individuals

make with each other an angle a= 2 (ft -90°' =7° 16'.

00

one of the twins (cryst. Nu. 4) the following determinations or
angles have been made.
Measured

Calculated

d: d =;a 20'

n: n =

3° 24'

73° 22'3° 30'

0

In colour leucosphenile is while inclining to greyish blue.
This shade does not, howe\'er, occur on crystal No. 8.

Purecrystals that have no cracks are often quite clear.

Often,

however, the leucosphenile crystals are traversed by cracks, orthey contain inclusions of extraneous matter; in such cases the~'a1'e somewhat opaque.

The crystalline planes as well as thefracture show a marked vitreous lustre. Certain faces, as thoseof the forms band n, often exhibit a pearly lustre.
In accordance with the monoclinic nature of the mineral
sections oriented parallel to the first and the third pinacoids
show extinction parallel to the second pinacoid.

But also asection cut parallel to the last-mentioned pinacoid shows extinction parallel to the direction of the a-axis. At all events thedeviation, if such there be, is so small that it has not beeDpossible to ascertain it. On the other hand, one of the extinction-directions makes, of course, with the vertical axis an angle=f1- 90° =3° 21' in the plane of symmetry. This direction

lies in the obtuse angle 11.

IU
The vibration - direction falling in the obtuse angle

P isthe optic normal, for the optic axial plane lies almost parallelto the third pinacoid. The first mean line (the acute bisectrix\coincides with the crystaUographic a-axis; and as this is at thesame time the direction of the greatest velocity of light, themineral is optically negative.
For the determination of the optic constants a natural anda prepared prism were used.

The former was bounded by thetwo faces (130) and (130) and bisected by the plane of thegreatest and mean velocity of light.

The refracting edge ofthis prism coincides with the crystallographic c-axis, but notexactly with the direction of the mean velocity of light of the['ubstance. The deviation, which is 3" 23'. as above stated, gh"esrise to an error in the determination.

It cannot, however,

exercise any influence of importance on the result.

The un-avoidable errors in using prepared prisms will probably in mostcuses be no less.

In the above-mentioned natural prism theindices of refraction a and p were determined by determining
the minimum deviation. The other prism is bounded on one
side by the third pinacoid and on the other by a cut andpolished face which makes an angle of 31 ° 42' with the said
pinacoid.

The refracting edge is parallel to the b - axis.

Inr, and again a, were determined by light

this prism the index

falling perpendicularly to the Orst-mentioned face. The following
values were obtained.

a{ira-rRed ..

1,6401

1,65i2

1,68290,0428

Yellow

1,6445

1,6609

1,68i80,0433

Green . . . . 1,64i5

1,6638

1,69230,0448From these values the follOWing axial angles are calculated

2Va =Red

Yellow

Green79° 26'

77° 4'75° 18'

IH
The dispersion is thus rather considerable and takes place
according to the formulap > v.
The specific gravity of leucosphenite has been determinedby weighing in benzole and found to be 3,06 \Mauzelius).
hardness is 6,0.

Its

The mineral has a distinct cleavage parallelto the second pinacoid b {o ID}.

The mineral is often easilycleaved in this direction; but in sections cut perpendicular lo
the cleavage, this is seldom quite distinct.

A cleavage parallelto the form " could not be detected, though the mineral onenshows a pearly lustre on the faces of this form.
As the material available was very scanty, no more than0,6238 gr. of pure substance could be procured for the analysis.

The analysis has been made by R. ~Ia u z e I illS; and the values
ohtained are as follon.
Molecular ratios
SiO~ .

56,9-1

0,943

10l1TiO~ .

13,20

ZrO~ .

3,50

0,165
0,025

BaO. ..va~O.

13,;00,090

0,0:>

Il,HK~O0,180 }
0,006

1,9;

0.56

HtO

0,31
---99,40

2.06

To obtain an acceptable proportion between the acid andthe basic constituents, Ti 0t and Zr 0., must be made basic.
The formula tben becomesB(l0.2S(ltO.2TitZrIO~.J08iO sor

B(I ..v(l.ITiOI~ \8i,0616.
Leucosphenite would thus be a dimetasilicate, and theonly known substance of analogous composition would be petalite. The lencospbenite cr~,.stals do. indeed, remind one in some

145
measore of the crystallized petalite from Elba. I have not,however, succeeded in 6nding any analogy between the crystaUographical constants of the two minerals.

On the other hand

there exists a partial agreement between the axial relations ofleucosphenite and e u did y m i t e.

This appears distinctly if

the a-axis of the former mineral he multiplied by three j one
then obtains
for leucosphenite: a: b : c = 1,7439: I : 0,8601 ;-a: b: c =eudidymite:

1,71076: 1 : 1,10712 j

f1 = 93° 23'

P=93° 45 1 /,'.

The angle f1 of the two minerals agrees very closely, and80

is also the case with the a-axes. The angles in the verticalzone are for both very near 60°, i. e. they are both in a sense
pseudo - bexagonal.

With both minerals twinning occurs withthe third pinacoid as composition-face. If the chemical formulaof eudidymite is written

then this mineral may be regarded as partially derived fromthe same silicic acid,H,Si, Or. ,whichmust be assumed to enter into the composition ofleucospbenite.

The two minerals cannot, it is true, be said to

be isomorpbous in the proper sense of the word, but it is anindisputable fact that there exists a remarkable analogy between
them crystallographically as well as chemically.
Before the blowpipe leucospbenite decrepitates and in
the forceps fuses witb some difficulty to a d ark globule.

Intbe salt of pbospborus bead a skeleton of silica is obtained j
on cooling the bead becomes opalescent.

Tbe mineral is de-composed by hydroOuoric acid, but not acted upon by otberacids.
The common leucospbenite has been met witb only at thelocality No. 2.
UIV.

On digging in tbis place a ratber considerable
10quantity of elpidite needles loosely agglomerated were found at
Bome depth below the surface. They had been protected fromthe atmosphere and were snow-white and tolerably fresh. The
mass was so loose that it could often be broken into pieces
with the hands. On pressure it yielded and fell asunder into
gravel with a crackling sound. The whole was traversed bylarger aegirine crystals, which thus formed a sort of skeleton
in the fragile aggregate. In the numerous spaces between theelpidite needles several other minerals occurred in crystals.
There were small well-developed crystals of epididymite, albite,polylithionite, leucosphenite, etc. The last mineral was fOUDd
only in small quantity. Like the other minerals mentioned here,
it is of later formation than the elpidite. Elpidite needles sometimes traverse the leucosphenite crystals, which, however, havebeen formed earlier than the albite. The crystal No. 8, which
is of a type differing from the others, was found on a specimen
from the locality No. I.

29. Elpidite.
By the name elpidite G. LindstrOm 1) designated a previously unknown mineral which he had observed in the LiiueD
collection. In his article he chiefly gives an account of theway in which he analyzed the mineral and the result oC hisanalysis. To the latter we shall return later on. L i n d s t r 0 m
further gives a statement of the physical properties of themineral as observed by him. Be describes it as finely columnar,forming long sheaves. Occasionally the columns are short andconfusedly intergrown. Sometimes they are malted together
into a half-compact, felt -like, brick - red mass. The mineraloccurs on aegirine crystals and sometimes fills up the drusy
cavities in which the latter occur. It is, further, accompaniedJ) GeoJ. Filren. FilrhandJ. Vol. 16, 1894, p. 330.

\