70728 - PETROGRAFIA

Learning outcomes

At the end of the course, the student will acquire the basic knowledge on the genesis, structure and composition of the main igneous, sedimentary and metamorphic rocks. Particular attention will be give to the main marbles, granites, porphyries and stones used in historical times.

In particular, the student is able to:

• recognize and classify, based on international recommendations, the main rock types used in cultural heritage;
• assess, on mineralogical-petrographic and structural grounds, the state of freshness / alteration of different rock types and stones;
• define, by direct observation of monuments, the nature and provenance of different rocks types and stones.

Course contents

What is petrography: aims and methods of study.

What is a rock: the rock cycle and the main petrogenetic processes. Brief reference of the main rock-forming minerals.

Igneous rocks: main physical features of silica magmas, their crystallization and evolution inside (intrusive igneous rocks) or on the surface (effusive igneous rocks) of the Earth. Recognition of minerals and structures on hand samples. IUGS classification (QAPF diagram).

Sedimentary rocks: general subdivision: clastic, chemical and biogenic sediments and sedimentary rocks. Classification schemes and recognition of components and structures on hand samples.

Metamorphic rocks: maim drivers of the metamorphic process, types and degrees of metamorphism. Classification schemes and recognition of minerals and structures on hand samples.

Petrographic study in laboratory: how to use a polarizing optical microscope, what is a thin section, recognition of the main rock-forming minerals and the effects of alteration under the microscope.

The UNI EN 12407 standard: Natural stone test methods - Petrographic examination.

The UNI EN 12440 standard: Natural stones. Denomination criteria.

The UNI EN 12670 standard: Natural stones. Terminology.

The main natural stones used in historical and monumental buildings.

Igneous rocks: Granite, Tonalite, Syenite, Diorite, Gabbro, Trachyte, Andesite, Basalt, Porphyry.

Sedimentary rocks:
clastic: conglomerate, breccia, sandstone, clay.

chemical: Gypsum rock, Travertine, Alabaster, Limestone.

biogenic: Calcirudite, Calcarenite, Calcilutite.

Metamorphic rocks: Slate, Phyllite, Serpentinite, Marble, Micascist, Gneiss, Amphibolite.

A course unit of 16 hours will focus on the petrographic study of natural stone materials used for architectural and ornamental aims in the Egyptian, Greek, Roman and Byzantine world.

Readings/Bibliography

Klein C., Philpotts A. (2018) Mineralogia e Petrografia (1a ed. italiana), Bologna, Zanichelli. (also in English language edition: check your favorite book provider to get a copy.)

Lazzarini L. (2004) Pietre e marmi antichi, Padova, CEDAM.

Teaching methods

• Frontal lectures
• Individual or group work on rock specimens and thin sections
• Short guided tours to sites of historical, artistic and architectural interest.

Assessment methods

The final exam aims to verify

(1) the acquisition of the basic petrographic knowledge of natural stone materials and

(2) the ability to apply this knowledge to the characterization of granites, marbles and stones used in ancient and modern heritage.

The learning assessment includes a two-hour practical test on stones of igneous and/or metamorphic and/or sedimentary origin, followed by an oral discussion.

The practical test consists in a technical-scientific written report that aims to ascertain the skills acquired in the classification and description of natural stones. The observations of three o more samples are performed on hand-sample scale.

 The instructors will assess the student's ability to recognize:

• The main rock-rock-forming minerals of the studied stone(s);
• The main structures and textures;
• The natural (e.g.: veins, inclusions, fractures, patinas ...) and artificial (e.g.: patinas derived from previous conservation interventions, type of surface finish) features that affect the stone appearance;
• The petrographic name assigned according to technical-scientific criteria;
• The tentative provenance of the material;
  

The oral discussion focuses on the student's ability to explain how the results of the practical test were achieved.

Grading:
Practical test: 50%
Oral discussion: 50%

For the final assessment, the following criteria will also be considered:

• correctness of the classification of the stone material
• appropriateness of the use of terminology;
• clarity of content presentation.

The demonstrated skill to recognize and critically evaluate different types of natural stone material will award excellent to very good marks.

Mnemonic knowledge of the subject, incomplete ability to synthesize and analyze stone specimens and not appropriate language will lead to marks between fair and pass.

Knowledge gaps, inappropriate language, difficulties in recognizing the stone material will result in an evaluation marked as barely passing, or not passing in case of important deficiencies.

Teaching tools

• Multimedia devices in lecture room
  
• Hand samples of different stone types
• Stereomicroscopes
• Polarizing optical microscope
• Web resources (e.g., Corsi Collection [http://www.oum.ox.ac.uk/corsi/] )

Office hours

See the website of Roberto Braga

See the website of Giuseppe Maria Bargossi

See the website of Gian Carlo Grillini