The Shells tell the Truth: Molluscs, some Stratigraphic Order and early Evolution

"He was painter, and he used his art to vividly depict his own concepts. So he depicts on the frontispiece the spirit of observation who, climbing on a mountain on which ground are spread marine bodies, shows one of those to a somehow surprised ghost, emerging from the mist, which seems not able to believe his own eyes."
Brocchi (1814) describing the work of his predecessor, artist and naturalist Agostino Scilla. Scilla in 1670 published “La vana speculazione disingannata dal senso”, where he argued that fossils are the petrified remains of once living beeings and one simply had to observe the similarities between the fossils and recent marine organisms in the field, instead of vain philosophising, to recognize this simple truth.

 

Fig.1. "Vanae Speculationis Sensus Moderator", a later published  (1752) Latin edition of Scilla´s work.

Italian mineralogist Gian Battista Brocchi (1772-1826) may not well known nowadays, but as both Charles Lyell as Charles R. Darwin were influenced by his works, he significantly contributed to forge modern geology.
He studied jurisprudence and theology in the Italian town of Padua, but soon became interested in geology, mineralogy, botany and zoology and will frequently combine or even merge his various interests. Brocchi, who studied also ancient Egyptian art, argued that certain cultural phases and art-styles first appeared in a rudimentary form, developed over time to become more elaborated and finally would become obsolete and replaced by other, more modern, art-styles. Strongly influenced by this observation he applied a similar approach to botany and zoology, where he compared recent species with fossil ones, noting that similar to cultural phases, also species can become extinct and are replaced over time by new ones.

Also in the mineral kingdom he observed an “evolution” of minerals over time, even more curious, he argued on a sort of “descend with modification”. In his "Trattato mineralogico e chimico sulle miniere del Dipartimento del Mella" (1807-1808) he explained the great varieties of minerals as derived from a set of more simple rocks - as he states - “evolved” slowly over time according to natural laws acting now as in the past (it´s not a coincidence that such ideas sound similar to Lyell´s later uniformitarianism).

His observations and research as inspector of mines in the recently established (1805-1814) kingdom of Italy was published in 1814 in the two volumes of “Subapennine Fossil Conchology”, where he also resumes all his geological as paleontological speculations. 

 

Fig.2. A somehow thoughtful Brocchi on the frontispiece of his book "Chonchiologia Fossile Subapennina con Osservazioni Geologiche sugli Apennini e sul suolo adiacente” (1814).

Volume one is an introduction, discussing stratigraphic as geological problems, volume 2 deals with the classification, description and distribution of Italian fossils found in Tertiary strata. Brocchi showed that different strata can be distinguished by the different species-assemblages, where the found fossil species become more and more similar to recent species as younger is the studied strata. Scottish geologist Charles Lyell, who was fluent in Italian and surely know of Brocchi´s work, will use the classification and distribution of fossil molluscs to define the geological epochs of the /former) Tertiary period. For Brocchi only the extinction of species and birth of new ones could explain the stratigraphic order he had observed. 

 

Fig.3. Fossil shells (bottom, Pliocene-Pleistocene) showing already some striking similarities to recent (top) shells of marine snails and bivavlves found along the Adriatic coast. Brocchi and later Lyell observed that with decreasing age of the geological strata more and more "recent" molluscs appeared in the sediments.

Unlike other contemporary naturalists like Comte de Buffon (1707-1788) and Georges Cuvier (1769-1832), Brocchi didn´t consider an external force (or catastrophes) necessary or responsible for the disappearance of a species from the geological record. Like a single human life or an entire culture, also a species would appear, evolve and thrive, but in the end vanish and disappear – it was inevitable and only a matter of time. Mammal species, appearing and disappearing quickly in the geological record, had a short “species-life”-expectancy. Molluscs, known for their longevity and also based on the observed stratigraphic range, had a longer life-expectancy and therefore slower faunal turnover. Brocchi surely know of Lamarck´s work on the fossil molluscs (completed in 1809) of the stratigraphic succession in the basin of Paris. Lamarck also subdivided geological strata based on fossil molluscs assemblages, but more important was an eager promoter of “variable species”. However from the contemporary reactions it seems that Lamarck´s s work was not well received. Lyell dedicated an entire volume of his "Principles of Geology" (1830) to rebut Lamarck´s hypothesis on transmuting species and Darwin considered the entire work of the French naturalist as "useless". Brocchi in contrast was at the time one of the few international recognized Italian naturalists and both Lyell´s uniformitarianism as the subdivision of the former Tertiary are based in part on Brocchi´s geological work. We know for sure that Darwin was strongly influenced by Lyell´s work and so surely came in contact with Brocchi´s geological ideas. Also some of Brocchi´s works on species evolution were translated into English and were probably discussed in lectures or in private meetings by the former teachers (like mineralogist Robert Jameson) of young Darwin.

Darwin during his voyage on the Beagle (1831-1836) wondered if species may die and are reborn in a discontinuous natural process.
Observing fossils similar to bones of the modern Mara (Dolichotis patagonum), a South American rodent that resembles a small deer, Darwin realized that species were replaced in time by similar forms. However the young Darwin didn´t yet consider a gradual transition of one species into another possible, as he frequently refers to the observed animals as “individual species” and distinct entities in time. Only some time later, influenced by Lyell´s  uniformitarianism, he will publish a more gradual model, where evolution doesn´t occur in jumps (as may suggested by Brocchi) but by slow and gradual evolution of populations. The distinct stratigraphic differences in species assemblages and the sharp limits between those, as used by Brocchi and Lyell to distinguish geological epochs, were for Darwin more an artifact caused by the"imperfection of the geological record" than by a supposed limited life-expectancy of a species. Species went extinct not for an organism-intern property, but simply because some species, by chance better suited to exploit the limited resources, would better survive and generate more offsprings and so over time replace less adapted species.

Bibliography:

CAPROTTI, E. (2010): Antiporte malacologiche del Settecento. Boll. Malacol. 46: 16-28
DOMINICI, S. & ELDREDGE, N. (2010): Brocchi, Darwin, and Transmutation: Phylogenetics and Paleontology at the Dawn of Evolutionary Biology. Evo Edu Outreach Vol.3(4): 576-584
DOMINICI, S. (2010): Brocchi’s Subapennine Fossil Conchology. Evo Edu Outreach Vol.3(4): 585-594

The Geology of Star Trek: II. It is not Life as we know or understand it!

It may surprise that there is no exact definition of what “life” is -  it is often described as a system in thermodynamic disequilibrium with it´s own environment and therefore forced to actively seek, incorporate and transform matter and energy. Part of the acquired energy and matter is used by this system to create copies of itself and so to survive it´s own death.

Some of these properties are however shared also by inorganic entities, like the order, growth or twinning of crystals, and a virus can´t grow or replicate without infecting a living cell.
 

"It is not life as we know or understand it!", Mister Spock in the episode „Operation Annihilate” and still from the episode “The Devil in the Dark”

Living bacteria were found in boreholes in 5.278 m depth, on the bottom of oceans, acid and toxic lakes, in hot springs with temperatures of 115°C and in rocks of Antarctica, thriving at -50°C.  Part of this success is explained by the molecular structure of these life forms, as carbon-based molecules are stable in a wide range of temperatures and in acid or basic solutions. 

Mister Spock is well aware of this fact:
 

“Life as we know it, is universally based on some combination of carbon compounds.”
 

However when the crew of the Enterprise is contacted in the episode “The Devil in the Dark” by the miners on Janus VI, supposedly attacked by an unstoppable “monster”, soon this fact is questioned. The creature can´t be tracked by the sensors of the Enterprise, nor by the tricorder and seems immune to direct hits with the phasers.
 

“But what if life exists, based on other element. For instance silicon.”
 

McCoy disagrees with Spock´s deduction, noting that it is a physiological impossibility, however Kirk agrees as it may improbable, but not impossible. Already in 1891 the German astrophysicist Julius Schreiner argued that silicon (Si) could replace carbon in molecules supporting complex chemical reactions and therefore a hypothetical metabolism. Three years later science-fiction author H.G. Wells speculated in an article of popular science about such life forms:
 

“One is startled towards fantastic imaginings by such a suggestion: visions of silicon - aluminium organisms – why not silicon-aluminium men at once? – wandering through an atmosphere of gaseous sulphur, let us say, by the shores of a sea of liquid iron some thousand degrees or so above the temperature of a blast furnace.”
 

In theory, silicon could form polymers and complex compounds together with metals or elements like boron, nitrogen, phosphorus and sulfur (in fact almost all known minerals involve silicon). Such molecules could work also in other liquids than water, liquids like liquid nitrogen, methane, ammonium, various alcohols and even acid solutions.
 

The Horta, as the mysterious native life form of Janus VI refers to itself, defends itself and digs tunnels in solid rock using a strong acid. It´s curious to note that certain acids, like sulfuric and hydrocyanic acid could act as solutions for an extraterrestrial metabolism.
 

However silicon as replacement to carbon has also it´s disadvantages. Complex silicon compounds are unstable and ineffective under terrestrial conditions. McCoy notes this, claiming that silicon life would not survive in the artificial (?) human environment created on Janus VI. But as it seems the creature called Horta comes from within the planet, where may suitable conditions exist. Silicon life forms may could exist in oxygen-free or poor  (as oxygen would oxides the silicon molecules), dry and very cold environments.  Such for humans highly prohibitive conditions would also reduce the metabolism and reproduction rate of this hypothetical life form, may we would not even realize that it is alive. In the Star Trek episode the Horta is the last of it´s kind, only the eggs – appearing to us like inanimate silicon-concretions - survive, however needing thousands of years to develop and be finally ready to hatch.
 

One of the great strengths of Star Trek was to pose both ethic as intriguing scientific questions, may some will be answered by future generations, when they one day may really encounter life, but not as we know it ... I find that a fascinating vision for the future!
 

Bibliography:
 

FOURESTIER, J. de (2005): The Mineralogy of Star Trek. Axis, Vol.1(3): 1 - 24
PICKOVER, C.A.(1999): The Science Of Aliens. Basic Books: 240
SHOSTAK, B. (2012): Life in the Universe. Addison-Wesley Publisher: 544
SCHULZ-MAKUCH, D. & IRWIN, L.N. (2006): The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. Vol.93: 155-172

The Geology of Star Trek: I. Minerals, Crystals and Alien Life Forms

„But a geological oddity to say the least. Pure silicon!“

„A few trace elements, look, we didn't you call here so you could collect rocks!“ 

Geologists get no respect, even if vital for entire civilizations, from the episode “The Devil in the Dark”.

According to Vulcan philosophy one should respond with grief only if a life was lost in vain. The loss of Mister Spock - more precisely of actor Leonard Nimoy – last week was followed by worldwide reactions, remembering him both in his role as a real person. I think Nimoy would have liked it, as it obviously shows that he left a lasting impression on our pop-culture.

So here is my geological-geeky tribute to his impersonation of the 1th science(including geology) - officer on board of the USS Enterprise and the geology of the Star Trek universe.
 

Geologists seem to be a quite common race in the Star Trek universe. According to "Star Trek - Enterprise" (and alluded in the movie "Star Trek: First Contact")  one of the first contacts of humans with an alien species occurred when the crew of a geological exploration mission crash-landed on earth and was forced to work in a coal mine in Pennsylvania.
This seems logical. Mining activities for raw materials and fuel are also widespread in the Star Trek universe. As every space-civilization would soon or later exhaust the resources of its own planet, there is an urgent need for specialists of extraplanetary geology.
 

Subterranean mining facility on Janus VI, essential for providing thousands of worlds with metals and other precious resources.
 

In many episodes of the original Star Trek series the crew of the Enterprise visits mining-colonies on foreign planets or searches for valuable minerals and crystals, there is even a geological tricorder available and how I did love to be able to access the mineralogical database in it. 
By convention the names of terrestrial minerals (a crystalline combination of one or various elements) end with the suffix "-ite", the denominations of elements with the suffix "- ium", "-um", "-on", "-gen" or "-ine". Unfortunately it seems that this nomenclature is not always applied with the necessary scientific accuracy by the Enterprise crew, but as those are (to us) unknown materials, it may be excused. 

Unknown elements, forming also unknown minerals, are not a scientific impossibility. The heaviest elements human science knows posses an atomic weight of 118. These elements are unstable and radioactive. However it may be possible that still unknown elements with an atomic weight, higher than 184, are stable and exist somewhere out there. 
Could these unknown elements form also minerals? Without facts it is vain to speculate. In meteorites we have found almost 300 different minerals, based on known elements, however formed under extraterrestrial conditions and therefore not found in earth´s environments. Iron-, magnesium-, calcium-silicates prevail, but also iron- and nickel-alloys, maybe forming also earth´s inner core but unknown on it´s surface.
 

More than 125 minerals are mentioned in the original Star Trek episodes, movies, animation series and the recent TV-reboots, however of these only 23 are actually real terrestrial minerals and only one mineral - olivine - has actually been found in extraterrestrial rocks. Curiously quartz, one of the most common minerals on earth, is almost never mentioned but specimens are used as props for dilithium crystals. In the Star Trek universe lithium or dilithium (spelling used in later episodes) is the only material that can be used in matter-antimatter reactors, standard equipment on board of federation spaceships. As its (supposedly) cubic crystal structure can filtrate antimatter it therefore can be used to control the energy output from the reactor. As some real minerals can filtrate or distort certain wavelengths of visibile light, it may be not a so far-fetched physical property after all.
 

Dilithium crystals are frequently referred in the original Star Trek series, also as gemstones, however they play a vital role in the episode "Elaan of Troyius". Here Mr. Spock and Scotty must repair the damaged energy converter of the USS Enterprise, a very delicate operation as they must rely on crude dilithium crystals, also the Klingons are attacking...
 

Gemstones like sapphires, diamonds, emeralds or rubies, all these crystalline forms have a great appeal to humans, but are just carbon, aluminium or silicon-oxide varieties ... quite illogical (from the episode “Cat´s Paw”).
 

Common salt plays an important role in the episode "The Man Trap" (it was also the first episode of Star Trek ever broadcasted, as the other episodes were rejected at first. In the original pilot episode, "The Cage", however there features also a geologist and a geological report). A remote outpost is infiltrated by a shapeshifting creature. Only using some halite (the mineralogical term for salt) as bait, the creature, in desperate need to feed on this mineral, will reveal it´s true form.
 

Collecting (literally) rocks in the Star Trek universe...

Sulfur, saltpeter and carbon (in two crystalline modifications, as coal and as diamond)  saved Captain Kirk´s life in the episode "Arena". Kirk is forced into a battle against the almost indistructible Gorn, a reptilian life form with armored skin. Only by using the naturally occurring outcrops of the mentioned elements and minerals on a desolate planetoid, Kirk is able to build a primitive gun. Using the sulfur, saltpeter and coal to make gunpowder and the pointy diamond-crystals as high-impact projectiles, he finally puts down his adversary for good (unfortunately the supposed "diamonds" have the wrong crystal shape).
 

However sometimes minerals can also cost a life. During negotiations for the mining rights of the rare but essential (and also non-existing) mineral topaline, a red-shirt is killed in the episode “Fridays Child” on the surface of Capella IV, just 32 seconds after beaming down…
 

He´s dead Jim, just 32 seconds after arriving on the surface of Capella IV …
 

It´s curious to note that hand lens or geological hammers are of no use in the 23th century. In the episode "Obsession" Spock analyzes a rock composed of the mineral tritanium with the already mentioned tricorder. Tritanium is 21.4 times as hard as diamond (curiously Kirk in the episode "Arena" states that diamonds are the hardest substance known in the Star Trek universe!?), therefore useful for the construction of indistructible spaceship hulls (which begs the question what phenomenon could erode and smooth the boulders found on the surface of Argus X). The rock can be sampled only by phasering off a piece, since it is too hard to cut with normal tools.
 

Shoot to sample...
 

However even the most sophisticated technology can´t replace geological intuition - It is not logical, but is often true. On Gamma Trianguli VI (episode “The Apple”) Spock immediately notes the lush vegetation, deducing correctly that also soil-nutrients and therefore geology plays a role in supporting this peculiar paradise-like world. With his sharp geological eye Spock identifies also hornblende and quartz in a rock (according to petrological composition may an igneous rock?), easily erodible (and explosive!) and so may the source of the rich soil.

But maybe the most fascinating incarnation of geology in the Star Trek universe is the encounter with silicon-based life forms (to be continued...)

Bibliography:

FOURESTIER, J. de (2005): The Mineralogy of Star Trek. Axis, Vol.1(3): 1 - 24
PICKOVER, C.A.(1999): The Science Of Aliens. Basic Books: 240
SHOSTAK, B. (2012): Life in the Universe. Addison-Wesley Publisher: 544
SCHULZ-MAKUCH, D. & IRWIN, L.N. (2006): The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. Vol.93: 155-172

On the Art of Mineral Identification

Hardness is an important feature used for mineral identification, but it is not the only one. 

Fig.1. Lecture in mineralogy, from Bartholomäus Anglicus "Über die Eigenschaften der Dinge" (1390-1400), on the Characteristics of Things.
 
May the chemist Torbern Bergmann (1735-1784) was one of the first naturalist to discuss mineral-hardness, however, as he believed that clay is also a mineral, he assumed that hardness was strongly influenced by the humidity of the environment and therefore not very useful. In 1784 the geologist A.G. Werner published his textbook "Von den äußerlichen Kennzeichen der Fossilien" (The external characteristics of fossils; fossils as anything excavated from the ground) introducing six hardness-degrees that could be distinguished with simple tools, like a knife, a file or steel-tools, all things available to miners or amateur rock-hounds. Mineralogist René-Just Haüy (1743-1822) introduced also test-minerals, like calcite (Mohs Hardness 3) and quartz (Mohs Hardness 7) for hardness identification. Finally mineralogist Carl Friedrich Christian Mohs published the modern 10-degrees scale in 1822.

 

 

Fig.2. Hornblende (Moos in Passeier, South Tyrol).

The streak, the color of the mineral-powder, is mentioned already by Georg Pawer (1494-1555), better known as Georgius Agricola, in his books on mining techniques. Also Werner considers the streak one of the most important features, where Mohs considers both streak as color of the crystal equally important. However it was Werner to introduce a classification scheme for crystal colors, using terms like steel-gray and apple-green to describe the colors of minerals.
Curiously to get the powder the crystal had to be crushed or damaged, only in 1865 streak plates were introduced.
 
Specific weight was used already by Arabic scholars to distinguish gemstones from fake stones.

 

Fig.3. Apatite (Lodner, South Tyrol). 

Also the reactions of minerals with chemical solutions can be very important. A sort of marble was known already as "Bitterspat", "Murakalzit" and "marble tardum" by Carl von Linné (1707-1778). However in 1791 the French naturalist Deodatus Sylvain Guy de Tancrède greatet de Dolomieu (1750-1801) noted that this rock doesn´t react with acid like common limestone and limestone-marble does. He published this observation and later the Irish chemist Richard Kirwan identified and named the new mineral dolomite - a Ca-Mg-carbonate.

Fig.4. Dolomite from the Dolomites, South Tyrol.

Today many other features, like magnetism, luminescence and radioactivity are used to identify minerals. However until the 18th century only some hundred minerals were known, mostly ores or gemstones, and the described identification methods were more than appropriated for everyday use.

Bibliography:

KORTINIG, S. (1988): Der Strich. Der Aufschluss, Jhg. 39: 221-225
KORTINIG, S. (1988): Die Härte der Minerale. Der Aufschluss, Jhg. 39: 371-378
KORTINIG, S. (1988): Die Farbe und der Glanz der Minerale. Der Aufschluss, Jhg. 39: 295-299
KORTINIG, S. (1988): Die Dichte der Minerale. Der Aufschluss, Jhg. 39: 376-378
MÜCKE, A. (1988): Die Seiten für den Anfänger. Der Aufschluss, Jhg. 39: 35-38

Mineral Classification Made Easy - Mohs Hardness Scale

Talc – Gypsum – Calcite – Fluorite – Apatite – Feldspar – Quartz – Topaz – Corundum – Diamond -  “Mohs Scale of Mineral Hardness ” should be familiar to rock-hounds and earth-science students alike, as it lists common minerals in the order of the relative hardness (talc as the softest and diamond as the hardest mineral). Almost all  basic classification charts include this scale, as mineral hardness can be a quite useful criteria to identify unknown minerals and can be easily tested in the field (a steel blade corresponds to fluorite and a piece of glass to quartz).

Mohs scale  is appropriately named after the German mineralogist Carl Friedrich Christian Mohs (lithograph by Joseph Kriehuber, 1832), born January 29, 1773 in Gernrode (at the time located in the principality of Anhalt-Bernburg), son of a middle-class family.

After school he worked in his father’s business as merchant, but in 1796 he went to the University of Halle to study  mathematics, physics and chemistry. He continued his studies at the famous Royal Saxon Mining Academy of Freiberg, where he studied under the even more famous geologist Abraham Gottlob Werner. Werner had published in 1787 a “Kurze Klassifikation und Beschreibung der verschiedenen Gesteinsarten” (Short classification and description of the various rock types), a classification guide that used – unusual at a time when most rocks were classified based on the complex rock-chemistry - easily recognizable features (like color)  to identify minerals and rocks.

Mohs was impressed by the approach of Werner and in 1804 published himself a “student-friendly” classification chart for minerals, based on his experience in the mining district of the Harz and as consultant for wealthy mineral-collectors.
In the work”"Über die oryktognostische Classification nebst Versuchen eines auf blossen äußeren Kennzeichen gegründeten Mineraliensystems” (The genetic-geological classification and an attempt to introduce a mineral-system based on superficial properties) Mohs combines various physical properties of minerals (like color, hardness an density) with 6 classes of crystal shapes  (in part in use even today) to identify 183 different minerals.

Fig.2. and 3. Specimens of Quartz (Mohs hardness 7) and Calcite (Mohs hardness 3), both minerals are common and can be very similar in shape and color, however they are easily recognizable by the different hardness, calcite can be scratched with a knife blade, quartz not.

After 1812, now as a professor in the Austrian city of Graz, he continued to improve his mineral classification scheme and to publish guidelines for mineral identification. In 1818 he succeeded Werner and became professor in Freiberg and between 1822-1824 Mohs finally published his famous hardness scale in the book  “Grund-Riß der Mineralogie” (Essentials of Mineralogy).

 
Bibliography:
 
HÖLDER, H. (1989): Kurze Geschichte der Geologie und Paläontologie – Ein Lesebuch. Springer Verlag, Heidlberg: 243
WAGENBRETH, O.(1999): Geschichte der Geologie Deutschland. Georg Thieme Verlag: 264

Geologists in the land of the Kangaroo

Terra Australis - the southern continent had been “discovered” by Europeans already in 1606, but only in 1642 the size of the new “island” becomes clear and the first geological observations  were made only in the early 19th century.

October 1800 two ships – the “Geographe” and the “Naturaliste” – set sail from the harbor of Le Havre, France. Under the command of Captain Nicolas Baudin (1754-1803) geographers, astronomers, artists, naturalists, zoologists, botanists, and 2 mineralogists – Louis Depuch (1774-1803) and Charles Bailly (1777-1844) – were instructed to explore, map and eventually claim for France new territories of this new world. In the last moment also the young zoologist, and trained paleontologist, Francois Auguste Peron (1775-1810) joined the expedition.

The geological observations made by Depuch (died during the expedition) are known from various reports send to Baudin. Bailly will publish some notes after his return to France and Peron included his research in the official report of the expedition.

In May 27, 1801 the bare land of Cape Leeuwin was in sight and the naturalists went on land along the Wonnerup Inlet, where they collected the first specimens of Australian animals, plants and rocks.

 

Fig.1. The “Baudin” – expedition, route drawn on Louis de Freycinet´s (1779-1842) “Carte générale de la Nouvelle Hollande”, published in 1811 as part of the results of the 1800-1804 expedition.

A storm forced the men to remain on land for several days and one man died during a failed attempt to reach the ships (during the entire expedition 32 men died, 13% of the crew, a surprising low percentage considering the period). The storm separated the two ships, the “Naturaliste” proceeded to the island of Timor, a Dutch colony at the time, where the crew fell ill with Malaria and other tropical diseases. The “Geographe” approached in November 1801 the island of Tasmania, where the expedition will stay for three months.
April 1802 the “Geographe” meet the British vessel “Investigator“. The expedition of the “Investigator” will map large parts of South-Australia and prove that Australia is one large continent, not two islands separated by a sea strait, as some geographers assumed. This was a disappointing discovery for captain Baudin, as there was no apparent geographic separation between the territories already claimed by British explorers, the entire continent had to be considered of British domain.

Captain Baudin, the crew and the naturalists could now only hope to gain some fame with the scientific results of the expedition...

The geologists Depuch and Bailly used a rock classification scheme, developed by the famous French geologist Déodat de Dolomieu, with four categories. They recognized primary rocks, such as granite; secondary rocks, such as stratified sandstone and limestone; alluvium (recent deposits) and volcanic rocks, such as basalt. The presence of these rocks in Australia was an important discovery, it proved that the classification scheme developed in Europe could be applied worldwide.

 

Fig.2. Charles-Alexandre Lesueur´s and Nicolas-Martin Petit´s depiction of Van-Diemen´s-Land for the “Voyage de decouvertes aux Terres Australes“. The two young men – unskilled workers at the beginning of the expedition -  were invited by Baudin to illustrate the logbook  -  both will become the most skilled artists for animal- and plantlife of the time. The granitic rocks found on the island of Tasmania convinced Peron and the other geologists that the most ancient – the primary – rock was Granite, forming the basement of all continents.

Paleontologist Peron noted along the west coast of Australia horizontal sand- and limestone layers (the Tamala-Limestone) and concluded, based on similarities to recent sediments, that these layers were deposited along an ancient beach, implying substantial variations in the sea level during geologic time:

“One of the greatest achievements of modern geology research and also one of its most indisputable, is the certain knowledge that, in the past, the level of the sea was higher than at the present time. At almost all places in the old and the new world is the proof of this phenomenon as numerous as it is evident. Only in les Terres australes was this still to be ascertained as, by virtue of its immense areal extent, it could have proved to be an important exception to the universality of the former domination of the ocean over the land.” 

(PERON & FREYCINET 1816)

Unfortunately the return to France will be disappointing for Peron. Captain Baudin dies on the island of Timor and French authorities will show little interest in the 220.000 samples of animals, plants and rocks, the 73 living animals, 3 kangaroos, 2 emus and 3 wombats brought back to Europe.

Peron publish his report “Voyage de decouvertes aux Terres Australes” only in  1807, after a long struggle for money and dies just three years later, before the completion of the second volume. However the sea shells collected during the expedition will be studied by an important French naturalist – Jean-Baptiste de Lamarck. In 1804 Lamarck publishes his theory about the transmutation of species, based in part of the observation that the fossil shells found in the sediments of France are similar, but not identical, to shells of living molluscs collected in Australia.

 

Fig.3. Peron discovers on the shores of Tasmania a living clam with a peculiar triangular shape – Trigonia antarctica – a genus of bivalve known only from fossils found in the sediments of the basin of Paris. He notes the similarities of this living specimen with fossil specimens – an important step to consider a relationship between fossil and extant species. Image of Trigonia sp. from Cretaceous sediments of Bavaria.

Unfortunately for Lamarck – and the naturalists of the Baudin expedition – he mixed his careful observations with wild speculations. Lamarck noted variations of organisms in time, however he could not explain why such variations occur or why certain organisms went extinct or survived – apart invoking a final cause and implying a sort of supernatural scheme. Geologist Charles Darwin will later regard Lamarck’s work as “useless“...

Fig.4. Geological map by Jules Grange, published in 1850, surprisingly little was known of the geology of Australia until the 20th century.

Bibliography:

GLAUBRECHT, M. & MERMET, G. (2007): Josephines Emu oder Die Geschichte einer vergessenen Expedition. GEO Nr.6/2007: 98-122
MAYER, W. (2008): Early geological investigations of the Pleistocene Tamala Limestone, Western Australia. from GRAPES, R.H.; OLDROYD, D. & GRIGELIS, A. (eds) History of Geomorphology and Quaternary Geology. Geological Society, London, Special Publications 301: 279-293
MAYER, W. (2009): The Geological Work of the Baudin Expedition in Australia (1801-1803): The Mineralogists, the Discoveries and the Legacy. Earth Sciences History Vol.28 (2): 293-324
RUDWICK, M.J.S. (2005): Bursting the limits of time – The reconstruction of Geohistory in the Age of Revolution. The University of Chicago Press, Chicago, London: 708

A tribute to the Year of Crystallography - Haüy´s Models

"It would be good if the readers, who wish to follow the details of these demonstrations, make themselves or have made, in cardboard or any other materials, solids that represent the principal varieties of crystals"
Haüy, 1784 - Portrait of French naturalist Haüy with contact goniometer, an instrument to measure the crystal angles. Haüy refused to use any other type of gioniometer during his lifetime, even if after 1809 high-accuracy optical goniometers, using reflection of light to measure the angles, were introduced.

The Danish anatomist and naturalist Nicolas Steno (1638-1686) was the first to note in 1669 that the faces of a crystal (2014 was also dedicated to the science of crystals) are always arranged in specific angles and crystals display a characteristic symmetry. Mineralogist René-Just Haüy (1743-1822) used a mechanical or contact goniometer to accurate measure the angles between the faces, realizing that all the various shapes of crystals could be reduced to just a limited number of basic geometrical shapes. In 1784 he published his observations in the book" Eassai d´une théorie sur las structures des crystaux", introducing the idea of seven basic unit cells. From a single "forme primitive" (the first unit cell) by adding other unit cells a crystal could grow (this concept predates also the modern theory of crystal nucleation).

Fig.1. Haüy´s seven unit cells, note the numbering, from "Eassai d´une théorie sur las structures des crystaux" (1784).

 

Fig.2. & 3. Wooden crystal model based on Haüy´s work, made in 1805 in Paris. As certain symmetries are repeated in crystals of a mineral, Haüy concluded that a mineral is made up by smaller, basic chemical units - he called them "molecule intergrante" - symbolized here by the small cubes, forming both a larger cube as a rhombus (both characteristic shapes of the cubic crystal system). More than 500-1000 wooden models were made after 1801, some sets commissioned by Haüy himself. Most models show simple crystals with smooth faces, only 20 complex models, showing the structure with the unit cells, survive.

 

Haüy´s work was quite influential for later mineral classification. In his popular book "Über die oryktognostische Classification nebst Versuchen eines auf blossen äußeren Kennzeichen gegründeten Mineraliensystems" (The genetic-geological classification and an attempt to introduce a mineral-system based on superficial properties, published 1804) the German mineralogist Carl Friedrich Christian Mohs (1773-1839) combines various physical properties of minerals (like color, hardness and density) with crystal models to identify 183 different minerals. 
From there the use of simplified crystal geometry to identify minerals was quickly adopted by other naturalists and the classification of crystals based on the seven unit cells / crystal systems of Haüy is still in use today.

Fig.4. Carl Linnaeus "Systema Naturae", published in 1770, in his work Linnaeus didn´t not only classify animals and plants, but also minerals. One element used to identify minerals were the various crystal shapes, here still displaying a confusing variability.