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THE JOURNAL OF GEMMOLOGY, 37(1), 2020 21
GEM NOTES
Imitations of Trapiche Ruby and Emerald
In October 2019, a concerned customer came to the
Netherlands Gemmological Laboratory with several
stones, each accompanied by a report from the Authentic
Gem Security Laboratory. This name did not sound
familiar, but according to the lab reports this organ-
isation is based in Delhi, India. The customer asked
us to check whether the issued reports were accurate.
Testing of some initial samples reported as ‘natural star
sapphire, heated, from Madagascar’, ‘natural sapphire,
heated, from Sri Lanka’ (in pink, purple and blue) and
‘natural ruby, heated, from Mogok’ showed that they
were synthetic corundum.
We also selected a ‘natural trapiche ruby from Mogok
(Burma)’ and a ‘natural trapiche emerald from Colombia’
for further study. Both of them had translucent areas
(pink to purplish red and bluish green, respectively)
together with opaque dark grey ‘matrix’ material. The
‘ruby’ specimen consisted of an oval slab measuring 26.97
× 22.93 × 2.56 mm and weighing 3.56 g (Figure 25a),
and the ‘emerald’ specimen was a round slab measuring
24.05–24.51 × 4.29 mm and weighing 5.02 g (Figure 25b).
The pink to purplish red areas of the first specimen
yielded a Cr spectrum and strong red fluorescence to
long-wave UV radiation, both typical of ruby. They had
rounded or hexagonal shapes and were heavily included.
Lamellar twinning showed comparatively random orien-
tations between the various areas, indicating they were
actually different pieces rather than part of a single crystal.
Raman analysis of these fragments with a Thermo Scien-
tific DXR Raman microscope using 532 nm laser excitation
focused slightly underneath the surface revealed Raman
and PL spectra typical of ruby. Small, orangey brown
inclusions were identified as rutile, confirming these ruby
fragments to be of natural origin.
The dark ‘matrix’ areas fluoresced strong whitish
blue to long-wave UV radiation (Figure 26). Magnifi-
cation revealed that they were not entirely opaque, but
contained abundant granular, dark angular fragments
and gas bubbles within a translucent to transparent
material (Figure 27).
Figure 25: The two samples reported here were originally identified as (a) ‘natural trapiche ruby’ (about 27 mm wide) and
(b) ‘natural trapiche emerald’ (about 24 mm wide). Photos by Dirk van der Marel.
Figure 26: Exposure of the supposed ‘trapiche ruby’ to long-
wave UV radiation produces strong red fluorescence in areas
corresponding to ruby and whitish blue luminescence from
the interstitial material. Photo by J. C. Zwaan.
a b
Figure 27: Microscopic examination of the ‘matrix’ material
of the ruby-bearing sample shows abundant small, dark
angular fragments and gas bubbles within a translucent
to transparent material. Photomicrograph by J. C. Zwaan,
brightfield illumination; image width 1.4 mm.
22 THE JOURNAL OF GEMMOLOGY, 37(1), 2020
GEM NOTES
EDXRF spectroscopy with an EDAX Orbis Micro-XRF
Analyzer, using a spot size of 300 µm, revealed that the
dark areas contained mainly Zr, Y and Si. At the surface of
the ruby areas, a high concentration of Si was measured.
Raman analysis of the small angular fragments confirmed
the presence of cubic zirconia in a matrix that produced
Raman bands characteristic of a mixture of resin and
silica (Figure 28), as seen in some imitation or ‘synthetic’
opals. These same Raman bands were observed at the
surface of the ruby fragments. We concluded that this
imitation of trapiche ruby was an assemblage consisting
of seven ruby fragments embedded in a resin-and-silica
‘matrix’ containing cubic zirconia grains.
The round slab with the green material was essentially
the same type of product—an assembled imitation of a
trapiche gem—although no emerald was detected. Raman
analysis of the green areas identified them as muscovite,
and EDXRF spectroscopy showed the expected presence
of major Al, Si and K, along with minor Cr and Fe. An
absorption spectrum viewed with a prism spectroscope
revealed a band at about 565–610 nm and a sharp line
at about 630 nm, which are consistent with the optical
spectrum associated with Cr3+ in fuchsite, a Cr-bearing
muscovite (cf. Reddy et al. 2003 and http://minerals.gps.
caltech.edu//FILES/Visible/Mica/Index.html).
Dr J. C. (Hanco) Zwaan FGA
(hanco.zwaan@naturalis.nl)
Netherlands Gemmological Laboratory
National Museum of Natural
History ‘Naturalis’
Leiden, The Netherlands
Reference
Reddy, S.L., Reddy, R.R.S., Reddy, G.S., Rao, P.S. & Reddy,
B.J. 2003. Optical absorption and EPR spectra of
fuchsite. Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy, 59(11), 2603–2609,
https://doi.org/10.1016/s1386-1425(03)00019-2.
Figure 28: Raman spectroscopy of the ‘matrix’ material (here, from the ruby-bearing specimen) showed bands typical for
a resin and silica mixture, confirming their manufactured nature.
Raman Shift (cm–1)
Raman Spectra
Intensity
