Gemmological study of the St. Wenceslas crown in Prague

Jaroslav Hyršl, Prague


The Czech king’s crown, named after St.Wenzeslas, was ordered by Charles IV and made between 1346 and 1387. The front side contains one sapphire, one rubelite, five spinels and one pearl. The right side is adorned by one spinel, six sapphires, an aquamarine and a pearl and the left side by a spinel, seven sapphires and a pearl. The crown's back contains two sapphires, fourteen spinels and a pearl. Four spinels are on the metal closure. Two bows on the top contain 25 emeralds, four spinels, fifteen rubies and sixteen pearls. The cross on the top includes a cross-shaped sapphire cameo, two sapphires and a spinel. Many stones, especially the sapphires, are of exceptional quality, seven of them have an estimated weight of more than 100 ct. The sapphires are probably from Sri Lanka, the spinels from Sri Lanka and Tajikistan. The source of emeralds remains unknown, the rubies are either from Sri Lanka or Burma (Myanmar), the rubelite may come from Afghanistan and the aquamarine from Sri Lanka.


Czech king’s crown, named after St.Wenceslaus, is the most important jewel in Czech Republic and one of the most important world’s jewels from the Gothic period. It has been considered to be a symbol of the Czech kingdom for centuries. Despite it’s unique gems it is almost unknown in gemmological literature. The reason is probably because the crown is not exhibited for visitors, but it is deposited in a special treasury in St.Guy cathedral in Prag’s Castle and is exhibited usually only once in five years for a few days. The first modern investigation of the stones was done by Kašpar (1947). The crown was later studied by J.Bauer and J.Kouřimský, but they redetermined only one stone and their results were not published. The last studies took part in 2.- 4. november 1998 and 2. and 14. july 2003 and was done by the author. 18 stones were redetermined during this study in comparison to Kašpar’s classic work.


Identification of stones in setting is very difficult anytime, because classic gemmological instruments as refractometer or polariscope can not be used. The crown weights 2,358 kg, has a diameter of 19 cm and its movement under a microscope was limited. Nevertheless, reliable results can be obtained from combination of several methods. The folowing instruments were used - dichroscope, spectroscope, thermal tester, UV-lamp, color filters including Chelsea filter and especially microscope Olympus with a fiber-optics ilumination for study of inclusions.


Front side

The front side of the crown is adorned by one blue and five red stones. The blue stone is a pierced sapphire measuring 52x35x12 mm, with a nice deep blue color I-1a. It’s weight is estimated to be 250 - 290 ct. The biggest central red stone (39.5x36.5x14 mm) I a was considered to be a ruby until this study, which prooved it to be rubelite, a red variety of tourmaline. The evidences for a determination are the lack of Cr-lines in a spectrum, the lack of fluorescence in UV UV-1 and a low thermal conductivity. It is a part of a natural crystal, a ditrigonal prism, which was broken perpendicular to the c-axis I-4 a. The stone has plenty of small fractures perpendicular to c-axis which cause its sheen. Along the surface are situated fine hollow tubes I-4 b and even curved cavities were seen in a microscope I-4 d. The remaining five red stones are all spinels. The upper one I-7 b (25.5x25x14 mm, about 100 ct) has top color and very good clarity and represents the best spinel of the crown.

Right side

The only red stone is a heavily fractured spinel. Six blue stones were identified as sapphires. The biggest one (39.5x28x11 mm, about 160 - 180 ct) II-2a has dark blue color and is one of the best on the crown. It contains a large pyrrhotite (?) inclusion with a metalic lustre II-2c. The other five sapphires have a lighter blue color II-3, four of them are pierced. The upper green-blue stone II-8a was considered to be sapphire, but in course of the recent study was redetermined as aquamarine thanks to its low thermal conductivity, lack of fluorescence in UV UV-2 and characteristic inclusions described below. It measures 27.5x26x15.5 mm and weights about 105 ct. It has many small oval fractures perpendicular to c-axis and very long yellow needles II-8 b. They were considered to be rutil in the past, but they are hollow tubes filled only partially by limonite II-8 c. The are not parelell to c-axis, therefore they represent most probably etched chanells, not growth tubes. In contrast to similar „needles“ in topaz (Koivula, 1987) they are not flat but have a circular cross-section.

Left side

The only red stone is spinel and seven blue stones are sapphires, four of them pierced. The biggest sapphire II-3 has 39x36x14 mm and about 260 - 280 ct. It was cut in a form of a very low pyramide. The second sapphire III-2a beside spinel measures 33x27x13 mm, weights about 190 - 200 ct an is very clean. The drill hole in the upper sapphire is covered by a small emerald III-8.

Back side

The only blue stone is sapphire IV-1a measuring 47.5x35x15 mm and weighing 300 - 330 ct. It is pierced in a cross-form and has a lot of veils. The other 15 stones were red originally, but only thirteen of them are red spinels, most of them pierced. The most interesting stones of this side are situated on a cluster right of a sapphire IV-2. The lower stone is a blue sapphire with a foil, which was red originally. The right stone was identified as almost colorless spinel, which was also originally underlaied by a red foil IV-2B a. It contains typical spinel inclusions, parallel rows of tiny octahedrons IV-2B b.

Four metal parts of the crown are joined by a metal closure, each is adorned by a pierced spinel. Four lilys are terminated by a big pierced white round pearl, the front one has diameter 14.5 mm. The holes in pearls are covered by tiny emeralds I-7 b.

The bows

The top part is composed of two bows with a cross on their intersection. The bows contain five big red stones, four of them are spinels and one is a ruby K-II-3. The ruby has even an asterism, but due to stone’s setting behind a lily a star is difficult to see. All fifteen small red stones were also determined as rubies, many of them contain typical inclusions as red rutile crystals, rutile needles, rutile silk K-I-6, black crystals K-III-3 etc. All 25 green stones are emeralds and 16 pearls are also present.

A cross-shaped sapphire Christ cameo Krizek measuring 25x20x4.5 mm is in the centre of the gold cross. It is pierced horizontally on its top but the hole is very difficult to see. A sapphire is situated on the top and two spinels are on sides of the cross.

Origin of crown’s gemstones


Kašpar (1947) has been determining an origin of sapphires to Ceylon and Siam (Thailand) according to their pleochroism and UV-luminiscence. It is not used in a modern literature anymore because of an overlap of those properties from different localities. But all inclusions in studied stones II-2b, III-2b, III-6 and IV-1b correspond well to those in sapphires from Sri Lanka (Gübelin and Koivula, 1992). Neither inclusions typical to Thailand were found, nor polysynthetic twinning. Thai source is also improbable from historical reasons, because first written notices about sapphire mining in Thailand are much younger, from 1548 (Hughes, 1997).


Spinels of the crown can be divided into two groups. First group is represented by bright red stones with common fractures and well-formed octahedral inclusions II-1. An example is the only spinel of the right side. This type of spinels is most probably from Sri Lanka as well as sapphires, but an origin from Tajikistan or Burma can’t be excluded. The second type of spinels has darker color (an old description is balas-ruby) and almost none inclusions, typical examples are on the front side beside the central rubelite I a. It comes most probably from Kukh-i-Lal deposit in Badakhsan in today’s Tajikistan (until recently it was incorrectly described as Afghanistan, because the locality lies exactly at the border between Afghanistan and Tajikistan) as well as famous Black Prince’s Ruby and Timur Ruby, both in London at present. Spinels were found in Badakhsan already in the beginning of our millenium (Hughes, 1994). Unfortunately, properties of those spinels are not described in a modern literature.


Kaspar (1947) assumed their origin from Egypt, because no other source was known in time of crown’s origin. But Egyptian emeralds were described recently by Jennings et al. (1993) and many emeralds from Egypt are known in Roman jewellery from many world’s museums. They are characterised by light green color with none or pink reaction in a Chelsea filter (very low Cr content), abundant fine parallel hollow channels and most of stones in jewellery are just polished hexagonal crystals. On the other side, emeralds of the crown have a deep saturated green color K-I-11 and are bright red in a Chelsea filter. Biotite inclusions typical for Egyptian emeralds were not observed and hollow tubes are only very rare on the crown. On the contrary, prism-shaped two-phase inclusions were found in several emeralds of the crown K-III-9.

Niedermayr (1991) described similar inclusions in an emerald from a Vienna Treasury. The emerald on a mantle from 12th century was found to be glued from two parts with completely different inclusions. One part has amphibol needles, apatite crystals and liquid inclusions, while bigger part with a good green color has prism-shaped two- and more-phase inclusions similar to modern stones from India. An origin of ancient emeralds from today’s Afghanistan is supposed also by Forestier and Piat (1998). From all those reasons, we also assume an origin of crown’s emeralds from Asia and not from Egypt.


Inclusions observed in small rubies are impossible to use for their origin determination, but two famous sources can be considered - Sri Lanka and Burma K-I-6K-III-3. Both have been well-known in time of crown’s origin.


The big rubelite is very similar to a big rubelite from Moscow, carved in a form of a bunch of grapes. This stone is known since 1570 and it’s history was described by Glas (2002). Source of Russian rubelite was determined as Burma by Russian mineralogist Fersman, but without any direct evidence. Much more probable is it’s origin in today’s Afghanistan, where similar stones are common recently and where old bussines routes between India and Europe were located.


The aquamarine, supposed to be a „green sapphire“ in the past, can be most probably from Sri Lanka as well as the sapphires. A similar type of dark aquamarine is known from there also recently (G.Zoysa, pers. comm. 1998).


Four oval pearls on the lily’s tops are large, symmetric and in a surprisingly good state I-7 a. They have a diameter between 14 and 15 mm. 16 almost round small pearls on the bows have a diameter approximately 7 mm each.

Cutting techniques

Faceting of gemstones is relatively young and most of stones in medieval objects has been used as natural pebbles, just polished on the surface. The first stones with symmetrical facets (but not in today’s sense, of course) appeared in Europe in the beginning of the 13th century (Lightbown, 1992). The crown has mostly irregular stones IV-2, many of them are pierced. Even a type of a hole has been changing from irregular, often splitted holes II-4 to perfect regular tubes as in the big sapphire on the front side I-1 a. Several stones exhibit primitive facets - three spinels on the front side I a (but their shape was predisposed by natural crystal shape), four sapphires on the right side II-4+5 and the biggest sapphire on the left side which has an unusual form of a low pyramid III-3. Those stones were probably fashioned shortly before an origin of the crown, while other stones had been probably used from older objects including a spinel necklace.


Forestier F.H. and Piat D.H. (1997): Émerauds de Bactriane: Mythe ou Réalité, La Valleé du Panjshir (Afghanistan). - in : L’émeraude, 139 - 146, Paris.

Glas M. (2002): The Kremlin‘s Carbuncle. – Tourmaline, extraLapis English No.3, 62 - 63.

Gübelin E. J., Koivula J. I. (1992): Photoatlas of Inclusions in Gemstones. - ABC Edition,

Hughes R.W. (1994): The rubies and spinels from Afghanistan - a brief history. - J. Gemm. 24, 4, 256 - 267.

Hughes R.W. (1997): Ruby & Sapphire. - RHW Publishing, Boulder.

Jennings et al. (1993): Emeralds and Green Beryls of Upper Egypt. - Gems&Gemology 29, 100 - 115.

Kašpar J. (1947): O drahokamech svatováclavské koruny. - Zprávy výzk. ústavu pro drahokamy v Turnově, č.6, 1 - 40 (in Czech).

Koivula (1987): The Rutilated Topaz Misnomer. - Gems&Gemology 23, 100 - 103.

Lightbown R. W. (1992): Medieval European Jewellery. - Victoria & Albert Museum, London.

Niedermayr G. (1991): Gemmologische Charakterisierung eines Smaragdes von der „Alba“ in der Weltlichen Schatzkammer in Wien. - Zt.f.Kunsttechnologie u. Konservierung 5, 2, 225 - 229.

Sinkankas J., Read P. G. (1986): Beryl. - Butterworths, London.

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