Volcanic stones (Pietre vulcaniche)
In this class I put together all those stones that were hurled from volcanoes and which are susceptible of taking a polish. Without concerning myself as to their composition I shall classify these stones according to their respective volcanoes and in indicating them I shall use the terms by which they are commonly known.
§ I Stones from Vesuvius (Pietre del Vesuvio)
621. (153.1) Lava of grey colour verging on sky-blue with some whitish veins. (Rare).
622. (153.2) Another of a slightly richer grey, with markings in the shape of eyes. (Rare).
623. (153.3) Another of darker grey verging on blue with blackish veins. (Rare).
624. (153.4) Another with a dirty white ground, and grey striations. (Rare).
625. (154.5) Another of dark grey with white lines. (Rare).
626. (154.6) Another of light grey with long lines of darker grey, and some of white. (Rare).
627. (154.7) Another of blackish colour with white lines and thick veins. (Rare).
628. (154.8) Another of grey flowered with white, and whitish knot-shaped markings. (Rare).
629. (154.9) Another almost white with a few sky-blue veins. (Very rare).
630. (154.10) Another of dusky grey with many small black spots. (Very rare).
631. (154.11) Dark grey ground with red, and glittering green markings. (Rare).
632. (154.12) Black ground with yellowish, and glittering green markings, all over. (Rare).
633. (154.13) Light apple green ground with a few glittering markings of darker green.
634. (154.14) Reddish ground tending to faded yellow, with small green and black needle-like lines. (Rare).
635. (154.15) Reddish ground with whitish waves, and markings of deep red. (Rare).
636. (155.16) Dark green ground with white, glittering yellow waves. (Rare).
637. (155.17) Olive green ground with a few reddish markings. (Very rare).
638. (155.18) Red ground with white breccie edged with black. (Very rare).
639. (155.19) Dark blush pink ground with small red, white, and black breccie. (Very rare).
640. (155.20) Rosy ground entirely covered with whitish waves. (Very rare).
641. (155.21) Black ground with many small dusky black spots. (Rare).
642. (155.22) Dark blush pink ground flowered all over with a lighter shade of blush pink and small white markings. (Rare).
643. (155.23) Dark grey ground flowered all over with a lighter grey. (Rare).
644. (155.24) Grey ground tending to dark blue, with many small black spots. (Rare).
§ II Stones from Etna (Pietre del'Etna)
645. (155.1) Reddish grey ground with very small white spots similar to oolite. (Very rare).
646. (156.2) Dark blush pink ground with white and glittering blackish markings. (Rare).
647. (156.3) Apple green ground with some reddish markings. (Rare).
648. (156.4) Coffee colour ground with many spots of red verging on yellowish. (Rare).
649. (156.5) Light grey ground with many markings of white verging on canary yellow. (Rare).
650. (156.6) Dark coffee colour ground flowered with white, and black. (Rare).
651. (156.7) Light yellow ground with many red markings. (Very rare).
652. (156.8) Purplish ground flowered with red and dirty white. (Very rare).
653. (156.9) Dusky grey ground with markings of light grey in the shape of crystals like porphyry. (Very rare).
654. (156.10) Monochrome of a beautiful brick red colour. (Very rare).
655. (156.11) Black ground with many very tiny purplish markings. Very beautiful and (very rare).
656. (156.12) Coffee colour ground spotted with red, and with white. (Rare).
657. (157.13) Reddish grey ground with lighter veins. (Rare).
658. (157.14) Deep grey ground with small black markings. (Rare).
659. (157.15) Dusky grey ground with darker markings verging on reddish. (Rare).
660. (157.16) Deep purpish ground with reddish spots. (Rare).
661. (157.17) Ash-grey ground with small white markings. (Rare).
662. (157.18) Dark grey ground with black, and white, spots. (Rare).
663. (157.19) Grey ground rich with black, and whitish, spots. (Rare).
664. (157.20) Blush pink ground with small black markings. (Rare).
665. (157.21) Blush pink ground with many white, black, and reddish spots. (Very rare).
666. (157.22) Light grey ground glittering with markings of greenish white. (Very rare).
§ III Stones from extinct volcanoes (Pietre de' vulcani estinti)
668. (158.2) Selce di Roma. Dark grey ground flowered with reddish. Quarried near the tomb of Cecelia Metellus, in the district known as Capo di Bove. The city of Rome is paved with this stone. (Very common).
669. (158.3) Another with a darker grey ground covered with very small whitish spots. (Rare).
670. (158.5) Vetro vulcanico. Obsidianum. Pliny 92 said that obsidian took its name from a certain Obsidius who first made use of it in Ethiopia. Isidorus Hispalensis 93 called it 'obsiano' almost as if it reflected images. Whatever the etymology of this stone may be, it is certain that the ancients used to think very highly of it, and used to regard it almost as a precious stone. Pliny 94 relates that under the principate of Augustus great amazement was engendered in Rome by four elephants of obsidian; and also that a statue of Menelaus, brought by Tiberius from Greece, which was considered prodigious. Obsidian is a volcanic product; in bulk it looks entirely black, but in [p159] small slabs and on the corners and it appears to be of a dark grey colour. It is often spotted with very small pieces of whitish feldspar. Obsidian was found in Ethiopia, and in abundance on Lipari. Lately it has been discovered in other places.