Corsi Collection of Decorative Stones

Class XIV
Quartz and its varieties (Quarzi)

This fossil is of remarkable hardness, and gives off sparks when struck by steel; it is generally of a white colour. Quartz is one of the most common stones: it is found massive, and scattered as pebbles, and it often forms the principal component of many rocks of either primary or secondary formation. Some modern authors have distinguished from common quartz, the amethyst, rock crystal, rose quartz, and aventurine. Since none of these fossils differs essentially from common quartz, however, excepting in colour, and they correspond in hardness, in crystal form, in specific gravity, in lustre, and in almost all other external characteristics, both in formation and in main constituents, they are therefore looked upon as simple modifications of common quartz.


Species I
Rock crystal (Cristallo di rocca)

711. (177) Mineralogists call rock crystal limpid. It is colourless, completely transparent, and its external characteristics are those of a beautiful and very pure glass. It can be distinguished, however, from glass by its greater hardness and the difference in its bubbles. When there are bubbles in glass they are round and dispersed irregularly throughout the mass, while those of rock crystal are extremely small and collect together within the same one plane. The largest rock crystal that there is in Rome weighs eight hundred and seventy pounds, and is in the possession of il sig. Giacomo Raffaelli the famous mosaicist and dealer of stones in via del Babuino no. 92. The specimen in the collection is wonderful for its purity and transparency, and it came from the Island of Madagascar. (Very rare).

Corsi's specimen does indeed have some bubbles aligned in planes as he describes, indicating that this otherwise perfectly transparent sample is crystalline and not an artificial glass. Rock crystal is the transparent variety of quartz. It has been carved, sometimes with extraordinary delicacy, since ancient Roman times, and was a particularly important medium before the invention of colourless glass. Rock crystal used in Europe originally came from Alpine localities, but it has been imported from Madagascar since the 18th century i .

i. Price (2007) 238

Species II
Amethyst (Amatista)

The colour of amethyst is usually violet, and comes from manganese. It is seldom found in large masses, and never has a compact texture because it is formed by the combination and enmeshing of a great number of crystals that give it a fibrous look. Crystals of amethyst are always more coloured at the points than at the bases. It is found in many places.

Corsi's observation that the colour of amethyst is deeper at the points than at the base of crystals is a useful one when identifying this purple variety of quartz. The colour does not come from manganese, but from a trace of ferrous iron. In Corsi's time, the main sources of amethyst would have been around Idar and Oberstein in Germany and the Ural Mountains of Russia, but the exceptionally fine amethyst of Rio Grande do Sul in Brazil had started to trickle onto the European market by this time i .

i. Price (2007) 239


712. (178.1) Amethyst of a violet colour verging on purplish formed of large crystals. (Rare).

713. (178.2) Amethyst of a white colour lightly tinged with violet formed of small crystals. (Rare).


Species III
Petrified wood (Legni pietrificati)

Whatever the theory of petrification may be, it is certain that masses of quartz are found bearing the colours, veins, and forms of not only the fibre, but the bark, and branches of trees, and to such an extent that the species of tree can often be recognised. Such stones are formed in many places. Near Cesena they are frequently seen widely scattered. One of their most distinctive characteristics is a noticeable lightness in comparison with other varieties of quartz. They are generally opaque, but transparent ones are also found. Their most common colours are white, black, red, yellow, and tawny; green is very rare.


714. (179.1) Dusky black ground, with some white marking. (Rare).

715. (179.2) Dark black ground with knots, and grey [p180] veining similar to the chestnut tree. (Rare).

716. (180.3) Gleaming white ground with peachy coloured and yellow veins similar to those of the white poplar. (Rare).

717. (180.4) Blackish ground with dark veins, verging on purplish. (Rare).

718. (180.5) Yellow ground with a large black marking. (Rare).

719. (180.6) Tawny ground marked with black in the form of dendrites. (Very rare).

Species IV
Aventurine (Avventurine)

Aventurine (avventurina) is formed of quartz reduced to minute particles. The most common colour of this stone is deep red verging on yellow; there are also some of white, and some of black. Its beautiful and distinctive characteristic is that of glittering caused either by the deposition of the lamellae themselves within the stone, or by the mixture of lamellae and of mica disseminated with great regularity and [p181] uniformity over the entire mass. This stone derives its name from artificial aventurine. Melted glass and brass filings were combined together by chance (per avventura), which resulted in a paste similar to the stone that hence, because of its unforeseen discovery, was called aventurine.


720. (181.1) Dark yellow ground with small white markings in the form of breccie. This specimen was cut from a fragment of a statue brought from Egypt. The particles are quite large, and similar to oolite. (Very rare).

721. (181.2) Red ground lightly flowered with whitish. This comes from Egypt. Mr. Dodwell, the English gentleman, possesses a beautiful piece of this stone carved with Egyptian hieroglyphics. (Very rare).

722. (181.3) Red ground with some yellowish veins more glittering than the other ones. This specimen comes from Siberia. (Very rare).


974. (Suppl.24.1) Quarzo erborizzato dell'Elba, entirely white, and on the underside covered with black dendrites. (Very rare).


Species V
Agate (Agata Achates)

The stone we call agate used to be called Achates by Latin-speakers, for according to Theophrastus 102 , it was first found near the river Acate in Sicily. This island is rich in agates, but later on it was also found in many other places: those of the East Indies are held to be the most beautiful. Brongniart 103 says they are formed like alabaster, and therefore they show very many lines of different tints. Agates change their names according to their colours. It is called onyx when it has white and black strata, chalcedony is that which is milk-white, sardonyx that which is dark, plasma the green, and carnelian the red, but they are only agates and have the same origins and the same characteristics. Agate is translucent; and may easily contain other substances that seem like images of recognisable things: there are also some decidedly dendritic agates. It is often found in combination with [p183] jasper. If the amount of agate is greater, it is called agate-jasper, but if it is less it is called jasper-agate.

'Achates comes from the river Achates in Sicily', wrote Theophrastus i . The Achates, now known as the Acate or Dirillo River, is in southeast Sicily.

i. Theophrastus 58, tr. Caley & Richards (1956) 52 §31


723. (183.1) Ancient white agate, partly clear and partly crystalline. (Very rare).

724. (183.2) Monochrome, of a white verging on milk-white. Commonly it is called chalcedony. (Very rare).

725. (183.3) Agata di Sardegna. Gleaming white ground covered with dark blue dendrites. Very beautiful and (very rare).

726. (183.4) Quarzo roseo compatto di Siberia. Rose coloured with black veins. (Very rare).

727. (183.5) Agata delle Alpi. Grey ground tending to faded yellow, with white veins. (Rare).

728. (183.6) Ground of reddish-grey agate with a few veins of red jasper. (Rare).

729. (183.7) Agata del S. Gottardo. Deep blue ground with reddish waves. (Very rare).


730. (184.8) Agata di S. Stefano in Sicily. Veined dark grey ground, with yellowish markings. (Rare).

731. (184.9) Agata di Giuliano in Sicily. White ground veined with yellow and purplish jasper. (Rare).

732. (184.10) Agata di Monte Reale in Sicily. White ground with markings of tawny coloured jasper. (Rare).

733. (184.11) Agata di Cefalo in Sicily. Cerulean ground with markings of deep yellow jasper. (Rare).

734. (184.12) Agata di Selinunta in Sicily. Dark ground with markings of golden yellow jasper. (Rare).

735. (184.13) Agata di Adriano in Sicily. Milk-white ground with markings of very light yellow. (Rare).

736. (184.14) Agata del fiume Drillo in Sicily. Crystallized white ground, with markings of jasper the colour of bricks. (Rare).

737. (184.15) Agata di Caccamo in Sicily. White ground with markings of deep yellow jasper verging on green. (Very rare). [p185]

738. (185.16) Agata di Giancavallo in Sicily. Ground partly gleaming white, and partly black, with markings of yellow shading into apple green. (Very rare).

739. (185.17) Agata di Milizia in Sicily. Gleaming white ground with small golden yellow markings. (Very rare).

740. (185.18) Agata di Volterra. Cerulean ground veined by canary yellow. (Very rare).

741. (185.19) Agata delle Alpi. Crystalline white ground with small markings of green jasper, that sometimes shades into reddish. (Very rare).

742. (185.20) Agata di Siena. Dark grey ground waved by lighter grey. (Very rare).


975. (Suppl.24.1) Agata bionda antica at the centre in a purplish breccia, and white verging on yellow. (Very rare).


Species VI
Jasper (Diaspro Jaspis)

Jasper used to be known to the ancients under the name of 'Jaspis' 104 . It is only a non-crystalline, opaque quartz, probably formed by watery deposition [p186] that exhibits all degrees of colour except fine dark blue, or violet. It is almost always veined and is seldom found monochrome. It is found associated with agate, and sometimes the names are juxtaposed as has already been noted. The most valuable is the blood-red jasper, especially if it should be from Persia, when it is called heliotrope.

§ I Ancient jaspers (Diaspri antichi)

743. (186.1) Red jasper similar to rosso antico. This type of stone was used by the ancients for engravings. (Very rare).

744. (186.2) Jasper with a purplish ground marked with both black and white agate, and sardonyx. (Very rare).

745. (186.3) Vivid red ground reticulated by white agate. (Very rare).

746. (186.4) Red ground marked with purple, with crystalline white agate. There is a vase of this precious jasper in the Galleria de' Candelabri in the Vatican Museum, no.1483. (Very rare).

747. (186.5) Dusky grey ground with tawny markings, and cerulean agate. (Very rare).


976. (Suppl.24.1) Diaspro d' Egitto. Pale green ground with markings of deep green, some of faded yellow, and others dark blue. This sample, obtained by me [suppl.p25] from Mr. Jarrett, was given to him by Earl Compton, of whom I made respectful reference in the Catalogue. Very beautiful and (very rare).

977. (Suppl.25.2) Another from the same place. Sapphire-coloured agate ground with red wood-coloured markings. (Very rare).

978. (Suppl.25.3) Another from the same place. Ground of white agate with markings of blood-red. (Very rare).


§ II Italian jaspers (Diaspri d'Italia)

748. (187.1) Diaspro della Tolfa near Civitavecchia. Light grey ground with grey veins like those in ruin marble that shade into red. (Rare).

749. (187.2) Another from the same place, with a whitish ground and grey markings. (Common).

750. (187.3) Resinite della Tolfa. Dark yellow ground with lines of different yellows. This stone is well known for its lightness of weight and for its conchoidal fracture with sharp edges. (Rare).

751. (187.4) Diaspro delle Alpi. Purplish ground with reddish markings. (Rare).

752. (187.5) Diaspro delle Alpi. Whitish ground with red markings in the shape of waves. (Rare).

753. (187.6) Diaspro delle Alpi. Purplish ground with green parallel stripes. (Very rare).

754. (187.7) Diaspro di Volterra. White ground verging on greenish with many gleaming white markings. Beautiful and (rare).

755. (187.8) Diaspro di Volterra. Dark yellow ground with markings of blood red. (Rare).

756. (187.9) Diaspro di Barga in Tuscany. [p188] Purplish ground with yellow veins that verge on red. (Rare).

757. (188.10) Diaspro di Barga. Purplish ground with gleaming white veins. The columns in the Borghese Chapel in S. Maria Maggiore are veneered with this stone. (Very rare).

758. (188.11) Diaspro di Volterra. Reddish ground veined with dark yellow, with a white mark that shades into canary yellow. (Rare).

The subtle shading of the jaspers from Monterufoli near Volterra, known as diaspro di Volterra, made this stone emminently suitable for portraying flower petals and shells in the pietre dure workshops of Florence.

759. (188.12) Diaspro di Volterra. Purplish ground with large yellow markings and white crystalline agate. (Rare).

760. (188.13) Diaspro delle Alpi. Light grey ground with waves of white and dark grey. Very beautiful and (very rare).

761. (188.14) Diaspro di S. Cristina. Mixture of cerulean, yellow, grey, and white. Beautiful and (rare). This and the following jaspers are all from Sicily.

762. (188.15) Diaspro di Misilmeri. Light green ground, with dark green, and faded yellow markings. (Rare).

763. (188.16) Diaspro di Adragno. Dark yellow ground minutely flowered with white agate. (Very rare). [p189]

764. (189.16) Diaspro di Giuliano. Dark yellow ground veined by green. (Rare).

765. (189.18) Diaspro di Castro Giovanni. Black ground with a large green mark in the centre. (Rare).

766. (189.19) Diaspro di S. Stefano di Bivona. Black ground with white, yellow, and reddish markings. (Rare).

767. (189.20) Diaspro di Giuliano. Green ground with yellow dendrites. (Rare).

768. (189.21) Diaspro di Solisano. Light yellow ground marked with dark yellow. (Rare).

769. (189.22) Diaspro del Piano de' Magli. Black ground flowered by purple with a few white veins. (Rare).

770. (189.23) Diaspro di Traina. Entirely dark grey that verges on faded yellow. (Rare).

771. (189.24) Diaspro di Giuliano. Deep red ground with veins of cerulean agate. (Rare).

772. (189.25) Diaspro di S. Stefano. Whitish ground with lighter markings. (Rare).

773. (189.26) Diaspro di Camerata. Half greenish colour that shades into strong yellow, and half emerald green. (Very rare).


774. (190.27) Diaspro di Giuliano. Deep red ground veined with white and flowered with blush pink. (Rare).

775. (190.28) Diaspro del Cassaro. Emerald green ground marked with faded yellow and whitish veins. (Rare).

776. (190.29) Diaspro di Palermo. Ground of white crystalline agate, with yellow markings edged with a scarlet red. (Rare).

777. (190.30) Diaspro di Coltabarro. Deep green ground, with spots and waves of a green that shades into yellow, and white veins. Very beautiful, and (very rare).

778. (190.31) Diaspro di Giuliano. Ground of white agate, with markings of blood red. (Rare).

779. (190.32) Diaspro di Giuliano. Green ground flowered by a blood red. (Very rare).

780. (190.33) Diaspro di Taormina. Deep red ground with lighter cloud shaped markings. (Rare).

781. (190.34) Diaspro di Moardo. Yellow ground marked by purplish edged with gleaming white. (Very rare).


782. (191.35) Diaspro di Monte Reale. Deep red ground veined with cerulean agate. Very beautiful and (very rare).


979. (Suppl.25.1) Diaspro delle Alpi. Light grey ground with markings of dark grey, and other ones of faded yellow. (Rare).

980. (Suppl.25.2) Diaspro di Sicilia. Deep red ground with markings of golden yellow. (Rare).

981. (Suppl.25.3) Another from the same place. Dark yellow ground with waves of other very diverse yellows. Very beautiful, and (rare).


982. (Suppl.26.4) Another from the same place. Light yellow ground with veins of agate. (Rare).