Gemmological Aspects of the Vila Pouca da Beira Monstrance in the Museu Nacional de Machado de Castro - Part 2

In this second part of the article, the gemmological content of the Vila da Pouca da Beira monstrance from the collection of the Museu Nacional de Machado de Castro, Coimbra, is discussed in light of the coloured gemstone production at the time of manufacture (early 19th century) in Portugal.




Monstrance
The artefact (inv. nr. MNMC 6904; O517) is a silver gilt radiant or sunburst monstrance that has been attributed to a manufacturing period in the first decade of the 19th century (1804-1810) at the workshop of Oporto goldsmith António Soares de Melo. Its original location was the Vila Pouca da Beira Convent, located half way between Coimbra and Viseu, approximately 270 km NNE of Lisbon, and became part of the Museum’s collection following the extinction of the religious orders by king Pedro IV in 1834. The vessel has a considerable size (74 x 31 cm) and is composed by two segments: a triangular section and elongated base, or stand, and a radiant ostensorium where a luna is kept to hold and exhibit the consecrated host. In the stand there is only one gemstone, a rather large citrine quartz, with a much splendorous gemmological content in the ostensorium, in line with what was common on such devotional implements where the greatest artisanship and materials acted as a way to dignify the Eucharist.

Gemmological Study
As mentioned in part I, only standard gemmological tools were used to identify the stones, namely magnifying lenses, colour filters, dichroscope, spectroscope, ultraviolet light and different types of light sources.  As expected, all gem materials were positively identified and verified.
The stand of the vessel only has one faceted gem, a large citrine quartz (63 x 57 mm), and this is noteworthy not only for its size, but also because on those days yellow quartz was not that common in Portuguese jewellery. The upper part of the artefact, the ostensorium, has a much richer gemmological content and due to its variety and number, the piece was segmented in different parts to enable an easier description: cross, radiant aura, ostensorium body (external rim), ostensorium body (interior), viril and lunette (luna).

Cross
The silver cross is adorned with rectangle shaped citrines, some with two cut corners, in open setting and both the gems and the setting are unusual for that period of attribution, suggesting a possible posterior modification. These opened settings, sometimes called “à jour” became increasingly popular throughout the 19th century as the then common closed settings were progressively abandoned. Two stones are missing, which enables a closer inspection of the metal settings.

Detail of the rectangular shaped citrines in open setting


Radiant aura
The aura is composed by 30 long and short sun rays, creating a sunburst effect, being totally covered with alternating pinkish-orange (14) and red (16) coloured gems (14 longer and 16 shorter rays, respectively). All the gems in scissor-like rectangular shaped cuts are set with a coloured foil back, a very common colour enhancement process that altered the visual appearance of those stones when in the setting. The gemmological properties of these stones, showed that 199 were yellowish topazes with red to pink coloured foils, causing an apparent orangey colour, and that 145 were amethyst quartz with red coloured foils, causing an apparent reddish colour. The true body colour of these stones, that is masked by the coloured foils, can be roughly perceived under the 10 x loupe in oblique observation angle.

Ostensorium Body (external rim)
The outer rim of the ostensorium is decorated with 17 yellow to orange topazes in cushion shaped cut and in closed setting with claws and metal rim (bezel setting with claws). A similar coloured foil back is easily detected under the stones, as in the 199 topazes on the aura. In some stones, internal cleavage plans with typical iridescent interference patterns can be readily seen under magnification, strongly supporting their identification as topaz. An oblique observation closer to the girdle shows that the body colour of these topazes is slightly different from stone to stone (as it is the case of the topazes set in the aura), but the coloured foil alters the face-up appearance, creating a more homogeneous monochromatic pattern. This effect is one of the reasons why such foils were used (the other being a colour enhancement to a more appreciated hue and tone), enabling colour consistency throughout the piece.

The body colour of this topaz can be seen near the setting on oblique observation. Note the pink to red colour of the foil.


Ostensorium Body (interior)
The inner part of the ostensorium has multiple gem-set applications, some of which are consistent with profane jewellery pieces, suggesting the re-use of these quotidian jewels on a devotional context, probably as ex votos (votive offerings that were given in order to fulfil a vow) or as part of a dowry from a novice to the convent. Deserving a special mention, there is a silver lace-pendant set with 105 rose cut and 2 table cut diamonds, where a tiny loop can still be seen, from where a pendent was probably suspended. A careful observation showed that two stones are missing, revealing the interior of the settings. The 105 rose cut diamonds are all of small dimensions and there are many irregular or rudimentary cut stones. The larger diamond has a full rose cut with the 24 triangular facets that were common on the popular Dutch rose cut. In spite of the late-seventeen hundreds’ design of this application, a period when the 58 facet brilliant cut became very popular, it was normal that smaller sized diamonds were still cut and used in the simpler and older rose cuts.

This diamond set segment is clearly a pre-existing jewel that was re-used in this devotional context.

There are various silver applications set with yellow topaz with a slightly coloured foil back that also seem to be jewellery that has been re-used. These topaz set monochromatic elements seem to have belonged to the same jewel that were separated into more than 17 individual applications in a design much similar to a 18th century necklace on display at the Museu Nacional de Arte Antiga, Lisboa (inv. nr. MNAA 6 J). The other gem set segments, also set with topaz with vegetalistic design, are most probably parts of profane jewellery artefacts from the same period. In total, there are 158 topazes set on these segments.
A total of 12 other small silver applications were counted as well. Each of these flower like segments are set with 3 topazes and 2 amethysts, all in pear shaped cuts, representing the petals and a rose cut diamond at the centre. The foil backs on these coloured gemstones show considerable age related alteration, thus revealing the true body colour of those stones. The quality of the diamonds is very modest, as it is their size, rudely fashioned in rose cuts and chips.

The coloured foils on the flower shaped application are degraded. The quality of the diamond is rather low. Note the green pastes in custom cuts creating a vegetalistic effect.


There are finally four metal leaf shaped applications with a much less refined manufacture and these are set with 18 custom cut green pastes, probably used as emerald imitations. These four elements seem to have been made to fit the monstrance and are not previously existing jewels that were introduced in the vessel as a re-use as many of the gem set segments already described.

Viril
The viril, that is the glass-faced receptacle made to display and protect the host, is richly decorated with colourless and high brilliance gem materials, suggesting the divine luminosity of the Holly Sacrament. This type of embellishment on the viril was very common on radiant monstrances of the 18th to 19th centuries. These colourless gems were identified as beryls that are known in the trade as goshenite (to be accurate, these beryls are not all absolutely colourless, as some display a very light bluish-green tint, witch means that these are more accurately described as very faint aquamarines). Colourless to near-colourless beryl can be easily and visually confused with the other three colourless materials, besides diamond, used on that period in Portugal: topaz, quartz and glass. Simple gemmological techniques combining different light sources, colour filters, ultraviolet light and magnification were enough to make a separation. A thermal inertia probe was used to cross check (the use of this instrument requires experience in interpreting the results). All these 36 beryls are set in closed setting and with a colourless reflective foil back, a slightly different enhancement procedure as here it is not the colour, but rather the brilliance and light return that is targeted. The culet is also painted with a black dot, a rather common subterfuge in colourless cut materials simulating the effect seen in old brilliant cut diamonds that was caused by the dark closed settings used on those days. An interesting feature of these colourless beryls is their cut in the shape of a shield, which was not very common at the time, suggesting a possible custom cut.
There are four other elements decorating the viril. Each of these flower shaped silver segments are set with six pear shaped red garnets (almandine-pyrope) and one round shaped cut colourless to near-colourless beryl. Despite the deep red colour of the garnets, there is an apparently coloured foil back underneath each stone.

The six garnets on this setting have colored foil backs. Note the colourless foil back and the painted black dot in the culet of the colourless beryl.


Lunette (luna)
The lunette, or luna, in the shape of a crescent moon is the removable part of the ostensorium where the consecrated host is placed for display and adoration. Due to the fact that it is the only part of the implement that contacts with the host, the gems set herein are usually of a much better quality. This lunette is decorated in both front and back with a rose cut diamond set rim. In the centre of this part there is a larger rose cut diamond, surrounded by smaller similarly cut diamonds. A closer look to the front of the lunette shows that the diamond set application is consistent with a profane jewel that was re-used in this devotional context. In total, there are 107 diamonds on the lunette.

The lunette is set with 107 rose cut diamonds. The central segment looks like a pre-existing jewellery piece.

Discussion
In total, there are 843 stones set on the monstrance, of which 18 are artificial products (glass), and the rest natural substances (393 topazes, 211 diamonds, 149 amethysts, 40 colourless to near-colourless beryls, 24 garnets (almandine-pyrope) and 8 citrines, one of which of a very large size). The number is not surprising in light of what was common in this type of devotional implements commissioned by wealthier individuals or communities.
The 211 diamonds, all of small size, are all fashioned in rose cuts, with a few exceptions of roughly polished chips and two table cuts. Only three diamond cuts show the 24 triangular facets of the traditional rose cut and these can be seen in the largest stones only.  No old brilliant cuts were encountered.
Coloured gemstones are much more common and most, if not all of them, of Brazilian origin. Topaz is the gem material in greater number, in a total of 393, and their body colours vary between the light yellow to slightly orangey-yellow. This variety of topaz is known to come almost exclusively from the Ouro Preto region of Minas Gerais, Brazil, since the second quarter of the 18th century and due to the special relationship with Portugal, the colonising country, it was very usual to see the material in large numbers in jewellery pieces, both devotional and profane. As it was common, a coloured foil was placed in the setting underneath the cut stone, enhancing the apparent colour and enabling a consistent colour homogeneity throughout the jewel. It is interesting to note that many of these topazes were part of a pre-existing artefact, most probably a necklace similar to the one previously mentioned and that resides at the Museu Nacional de Arte Antiga in Lisbon.

The ostensorium seems to have been embelished with parts of a 18th century topaz nacklace like this one at the Museu Nacional de Arte Antiga, in Lisboa © MNAA/DGPC


Quartz is well represented in two of its popular varieties: amethyst (violet) and citrine (yellow). The 149 amethysts all seem to have light body colours that are masked by the colour of the reddish foil back that is applied in the setting. This was a common practice. The citrines are quite odd, as they are not common gemstones in Portuguese jewellery of this period, nor, in the case of the upper cross, are they cut and set in a traditional manner. This suggests a probable modification of the top of the monstrance on a later date, but no documentation supports that possibility. A special mention must be made to the very large citrine at the stand of the vessel, being on of the largest cut gemstones in Portuguese collections.
The colourless gemstones on the viril of the monstrance are noteworthy. Usually, besides glass, it was topaz, but specially quartz (rock-crystal) that were used for this purpose (also diamonds in special commissions). In this artefact, it is colourless to near-colourless beryl with a very faint greenish-blue tint, displaying the characteristic high brilliance of this gem material. A colourless foil is applied to every setting, as well as the usual black dot in the culet. In Portugal, these colourless gemstones have been known in the antiques trade as “minas novas”, a name that also covers quartz and topaz, hence not an accurate gemmological trade term. A total of 24 red garnets of the pyrope-almandine isomorphic series is also present and curiously enough, despite their deep colour, a coloured foil is backing all these stones.
As artificial products, 18 custom cut green pastes (glass) were identified. An affordable way to get green cut stones was, in fact, the selection of green pastes, much more convenient and available than quartz/green cement/quartz composite stones that are known in Portuguese jewellery of the same period. Emeralds, of course, were much more expensive and not that readily available on the local market at the time.
One of the more interesting aspects of this remarkable monstrance is the use of pre-existing jewellery as decoration. As mentioned before, it was a common practice to introduce those jewels or their segments in devotional artefacts as most of these were ex votos (devotional offerings) or even part of dowries from novices to a convent, as was the case of the original location of this vessel. From an historical point of view, these jewels or segments are important testimonies of the different profane typologies and their gemmological content that predate the manufacture of the implement.

Conclusion
The gemmological content of this devotional implement is consistent with its period of attribution (1804-1810), as both the natural and artificial stones, as well as the settings, were known and used on that period in Portugal. Brazilian coloured gemstones (topaz, amethyst, citrine, beryl, garnet) are very well represented as well as diamonds of a much probable Brazilian origin as well. Portuguese jewellery of the second half of the 18th century until the first quarter of the 19th century is rich in these Brazilian coloured gemstones and diamonds due to the fact that Brazil was a colony of Portugal until 1822. The decoration of a devotional implement with pre-existing profane jewellery pieces, probably as ex votos or dowries from novices, is quite common and there are many other examples in Portugal.
For all that matter, standard gemmological techniques such as magnification, colour filters, dichroscope, spectroscope, ultraviolet light and thermal probe, have proven to positively identify all the materials in this historical artefact showing that simple and affordable gem testing is still effective in delivering gemmological identification reports on particular situations. Knowing the limitations of the techniques and having a sound training and experience is key to the gemmologist.
The monstrance of Vila Pouca da Beira, along with a vast and very interesting jewellery collection, can be visited in the Museu Nacional de Machado de Castro, in Coimbra (http://www.museumachadocastro.gov.pt/en-GB/default.aspx)


adapted and translated from Galopim de Carvalho, R. et al. (2011) “A Custódia de Vila Pouca de Aguiar” in Normas de Inventário - Ourivesaria (pp. 162-171), Instituto dos Museus e da Conservação, Lisboa

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