March, 2009
B”H
Roup A., Kalmanovitch E., Baykov Y., Toledo V.
Shefa Yamim (A.T.M.) Ltd., 90 Herzel St., P.O.B. 720, Netanya – 42106
Web site: www.shefayamim.com
E-mail: [email protected]
Geological occurrence: Moissanite, as a native silicon carbide is a very rare mineral, predominantly found (in small amounts) only in kimberlites (Yakutia, Central Asia, Ural Mts., Archangelsk district, Finland) and
in meteorites (Diablo Canyon). A new find hosted in serpentinite has recently been reported from the Dabie Mountains in China (Shutong Xu. et al., 2008). One unique specimen was found at a beach along the
Turkish coast of the Mediterranean Sea around 150 km NW from Izmir and is most likely derived from Tertiary volcanic rocks outcropping in the area (Rock-Forming moissanite (natural -silicon carbide) S. D.
Pierro, et al 2003). In addition, 14 blue-green grains of moissanite and 2 diamonds were found in the lamprophyric breccia by Cabo Mining in Canada. Discoveries have shown that moissanite occurs naturally as
inclusions in diamonds and xenoliths and in ultramafic rocks such as kimberlite and lamproite (Di Pierro et al., 2003).
During Shefa Yamim exploration and prospecting activities, SY found this rare mineral in drill cores, and in samples taken from the up-surface of various magmatic
bodies on Mount Carmel. The crystals found ranged in sizes from 0.1mm to 2.2mm. More than one thousand pieces of moissanite were recovered in the area of the SY
licenses. This finding was made while drilling for diamonds in which 77 micro and macro diamonds have been found to date. 76 diamonds were found within drill cores in
the Kishon graben sedimentation and 1 diamond in the Rakefet Magmatic Complex (RMC) (De Beers, May 2004).
The colors of the moissanite grains varies between black, yellow, dark blue, blue green, green-blue, grey and colourless. Moissanite grains were found associated together
with large amounts of "Kimberlite Indicator Minerals" such as pyrope garnet, chrome-spinel, ilmenite, clinopyroxene (chrome-diopside), rutile etc'.
The result of 8 X-Ray tests (Chemical Department, Technion, Haifa, analyst Dr. M. Botoshansky) show that unit cell parameters of all examined samples ranges
a=3.0794-3.0810 (average 3.0806) and c=15.111-15.161 (average 15.125), c:a= 4.909 with primitive hexagonal symmetry. These crystallographic parameters are typical for
moissanite and characteristic of the 6H polytype. This typical moissanite modification is dark-coloured, hexagonal (6H-polytype), and usually occurs in association with
diamond, corundum, pyrope, Mg-rich olivine (forsterite) , and Cr-spinel in kimberlite pipes and alluvial placers.
The presence of moissanite indicates extreme reducing and ultra-high pressure conditions also favorable for diamond formation. Thermodynamic and thermochemical
data indicate the existence of moissanite in the P-T range of 1100-14000 K and 2.0-16.0 GPa in a Fe-free peridotite composition.
Despite the fact that results of SEM analyses of grains of moissanite may not always be 100% accurate concerning the variable Si/C ratio, according to Dr. Y. Levin and
In 1893, Nobel-Prize winning
Dr. P. Mukhin (November 2001) the chemical composition of more than 100 moissanite grains, which were analyzed by SEM (IGS, Jerusalem), shows a variable Si/C ratio of
scientist Henri Moissan began
the analyzed samples. This indicates that the moissanite grains contain excessive carbon and silica free phases from 5-6% average, compared with a theoretical moissanite
studying fragments of this
composition (Si-70.04 %, C-29.96 %).
meteorite from nearby Diablo
Canyon. In these fragments Dr.
Moissan
discovered
minute
quantities of a shimmering new
mineral, with fire and brilliance
never before seen on earth. After
extensive research, Dr. Moissan
concluded that this mineral was
made of silicon carbide. In 1905,
this
mineral
was
named
moissanite, in his honor.
Inclusions in moissanite (sample 59)
Green crystal (olivine?)
Dodecahedrons (garnet?)
Olivine?
Gauze-liquid inclus
Long incl.(rutile? olivine?)
Blue crystal. Anisotropy and isotrop.
Name:
moissanite
Synonyms:
Carborundum, Silicon Carbide
Chemical Formula:
SiC
Special gravity (g/cm3):
3.1 – 3.2
Hardness:
9.25 – 9.5
Luster:
Adamantine, metallic
Color:
Black, blue, green, green-yellow, colorless
Diaphaneity:
Opaque to transparent
Refractive Index (brilliance):
2.65-2.69
Crystallography:
Hexagonal and Trigonal polytypes
SY Moissanite in host rock (15% Moissanite content)
Physical properties: moissanite belongs to the hexagonal crystal system, space group is P 63mc; cleavage is indistinct; refractive index of 2.65–2.69; density of 3.22 g/cm³; hardness of 9.25 and varies in
colour including clear, greyish green, greyish yellow, grey, greenish yellow, brownish yellow and yellow green (Read P. 2005). Moissanite is stable to temperatures up to 1127 °C (1400 K) and can
withstand pressures up to 52.1 GPa (Xu J. and Mao H., 2000). These properties make moissanite unique. Silicon carbide has a wide, adjustable bandgap, giving the mineral variable conductance
properties, which are useful in nanotechnology (Melinon P. et al 2007). Moissanite belongs to the carbon group and because of its similarity to diamonds it is used as a replacement for diamonds in
fashion and in scientific applications.
Sample 602
3.5mm
Diamond and Moissanite Distribution in some of the Shefa Yamim drills
Moissanite(2mm)
Moissanite(+2mm
)
Diamond
“… One of the most indicative peculiarities of the Shefa Yamim
moissanite grains is systematical enrichment with free carbon,
which seems to be a solid phase and/or minor diamond
inclusions.The large quantity of moissanite in the host rock of the
Kishon river placer indicates undoubtedly about deposition of
diamonds at the same stratigraphic level... It promises, in addition
to high concentration of small grains of moissanite, that there is a
good chance to discover unique commercial deposit of moissanite
(in the sizes and commercial amounts) in the Shefa Yamim license
area. The potential’s of the Shefa Yamim license area will
incredibly increase, if large crystals of moissanite are found",
quote from "Moissanite – New Mineral Findings in the Shefa
Yamim Licence Area” by Dr. Pavel Mukhin and Dr. Yaakov Levin
(November 25, 2001).
Sample 321
Moissanite is found within the sedimentation along Emek
Yisrael and into the Zevulun Valley and almost to the
Mediterranean Sea (both sides of the Kishon River) – as well
as along Nahal Zippory. In addition, large amounts of
moissanite crystals were found within the Rakefet magmatic
complex (RMC). Nahal Rakefet flows into and joins Nahal
Yokneam; our largest moissanite discovery (3.5mm) was
made in the drainage area within the sediments of Nahal
Yokneam. There seems to be a "pattern" of findings in a
South to North direction.
There is no doubt about moissanite occurrence in the
upper cretaceous magmatic bodies, such as: Rakefet,
Kerem Maharal, Shefeya.
© Mendy Design
Sample 216