4.20 ct Untreated Richterite Sugilite AAA Gel Translucent Cabochon Gemstone

Description

Untreated Gel Quality Richterite / Sugilite Cabochon- Wessels Mine - South Africa
This stone was cut from rough material  purchased in Kuruman, South Africa in the late 90's
Today rough stone is getting more difficult to find in this quality due to the mines restrictive policies
Pictures are taken with 5500 K daylight lamps and back lighting to show translucence
Kindly note that pictures are enlarged and inclusions are more visible, contrast and colour can differ slightly from original
Size : 11.8 x 9.8 x 4.2 mm            Weight : 4.2 ct
This cab has an interesting hematite inclusion
********************
Examination of jewelry-quality sugilite shows that it consists of manganese-bearing sugilite and other minerals in a polycrystalline aggregate. The material occurs in a large stratiform manganese orebody at the Wessels mine near Kuruman, South Africa. Some 12 to 15 tons of sugilite of varying quality are estimated to occur at the mine. The attractive purple color is due to the presence of about 1-3 wt. % manganese oxide. The research reported here revealed that there are actually two types of gem materials that have heretofore been called sugilite: one that is predominantly manganoan sugilite with minor impurity minerals, and the other that is chalcedony mixed with (and colored by) sugilite.
********************
Sugilite
Sugilite from Wessels Mine in
Northern Cape Province
,
South Africa
General
Category
Cyclosilicate
Formula
(repeating unit)
K
Na
2
(
Fe
,
Mn
,
Al
)
2
Li
3
Si
12
O
30
Strunz classification
09.CM.05
Dana classification
63.02.01a.09
Crystal symmetry
Hexagonal
Identification
Formula mass
1,041.66
Color
Light brownish-yellow, purple, violet, reddish violet, pale pink, colourless
Crystal habit
Granular
Mohs scale
hardness
6–6½
Luster
Vitreous
Streak
White
Diaphaneity
Transparent to translucent
Specific gravity
2.74
References
[
1
]
[
2
]
Sugilite
(also known as
lavulite
) is a relatively rare pink to purple
cyclosilicate
mineral with the complex chemical formula
K
Na
2
(
Fe
,
Mn
,
Al
)
2
Li
3
Si
12
O
30
. Sugilite crystallizes in the
hexagonal
system with prismatic crystals. The crystals are rarely found and the form is usually massive. It has a
Mohs hardness
of 5.5 to 6.5 and a
specific gravity
of 2.75 to 2.80. It is mostly translucent.
Sugilite was first described in 1944 by the
Japanese
petrologist
Ken-ichi Sugi
(1901–1948) for an occurrence on Iwagi Islet,
Japan
, where it is found in an
aegirine
syenite
intrusive
stock. It is found in a similar environment at
Mont Saint-Hilaire
,
Quebec
,
Canada
. In the Wessels mine in
Northern Cape Province
of
South Africa
, sugilite is mined from a
strata-bound
manganese
deposit. It is also reported from
Liguria
and
Tuscany
,
Italy
;
New South Wales
,
Australia
and
Madhya Pradesh
,
India
.
Note: The mineral is commonly pronounced with a soft "g", as in "ginger". However, as with most minerals, its pronunciation is intended to be the same as the person it is named after; in this case, the Japanese name Sugi has a hard "g", as in "geese":
/
ˈ
s
uː
ɡ
ɨ
l
aɪ
t
/
SOO
-gi-lyt
.
Contents
1
Gallery
2
See also
3
References
4
External links
Gallery
[
edit
]
A rich thumber of pretty purple sugilite on a matrix of
bladed
barite
crystals, Wessels Mine in
Northern Cape Province
,
South Africa
, size: 2.4 x 2.1 x 1.2 cm.
See also
[
edit
]
Earth sciences portal
Classification of minerals
List of minerals
List of minerals named after people
References
[
edit
]
Jump up
^
Webmineral
Jump up
^
Mindat.org
External links
[
edit
]
Wikimedia Commons has media related to
Sugilite
.
R. V. Dietrich
Mineral galleries