1526) About Minerals and Rocks, Croatia: A set of two Stamps of 5 HRK each depicting the Hrascina Meteorite and the Lithothamnium Limestone issued by Hrvatska Posta (Croatian Post): Date of Stamp Set issue: 22.10.2020:
The study of Rock Formation and classification is called Petrology, and the study of Minerals that the rocks are composed of is called Minerology.
Rocks form the solid outer shell of the Earth, known as the Lithosphere, which consists of the crust and the solid outermost layer, and reaches up to 100 kilometres in depth. The Mantle extends to a depth of 2,900 kilometres underneath the Lithosphere, while the Core continues to the centre of the Earth, to a depth of 6,370 kilometres.
Rocks are aggregates containing one or several types of minerals.
Minerals are the products of natural physical and chemical processes and are characterised by a specific chemical composition and crystal structure, which is stable at certain temperatures and pressures. The minerals regular internal structure reflects on their external form too. Such types of minerals are called crystals.
In terms of formation, Rocks are grouped into - Igneous, Sedimentary and Metamorphic.
Igneous Rocks account for about 95% of the Lithosphere, and the other two types accountfor the remaining 5%.
Rocks composed of a single mineral are referred to as monomineralic, while rocks composed of several different minerals are referred to as polymineralic.
There are more than 4,700 minerals known today, which are grouped into 14 classes by their chemical composition and structural properties - native elements, Sulphides, Halides, Sulphosalts, Oxides and Hydroxides, Carbonates, Nitrates, Borates, Iodates, Sulphates, Phosphates, Arsenates and Vanadates, Wolframates and Molybdates, Organic compounds and the large group of Silicates which make up more than 95% of the Earth's crust.
The Stamps:
.About the Hrascina Meteorite:
The Croatian Natural History Museum's collection of extraterrestrial materials (Meteorites) comprises some fifty exhibits from all over the world, but specimens that fell in Croatia (Hrascina Miljana and Dubrovnik)are of special interest.
The Hrascina Meteorite, also known as "The Zagreb Iron", has a special place in the collection.
This iron Meteorite fell in the village of Dumovac near Hrascina in the region of Hrvatsko zagorje on 26.05.1751 at about 6.00 pm.
Meteorites are fragments of a space object - such as a comet, asteroid or meteoroid, which survivethe passage through the atmosphere and fall on the Earth's surface.
Meteorites are divided into three main groups - irons, stones and stony-irons.
Unlike stony meteorites, which resemble the Earth's rocks, iron meteorites have a higher nickel concentration than the iron found on Earth. The Hrascina Meteorite played a key role in discovering this fact.
Vienna based factory owner Alois von Widmannstatten tested the Hrascina Meteorite by etching a polished slab of the meteorite with Nitric Acid, which brought out lattice-like patterns.
The patterns (lamellae) that have since been used as the basis to differentiate between terrestrial and extraterrestrial iron are called Widmannstatten patterns and they occur due to the separation of the mineral Kamacite (Fe and up to 7% Ni) and Taenite (Fe and 24-40% Ni).
The Hrascina Meteorite is important, because its fall was recorded in the first official report about the fall of a meteorite in history. On 06.08.1751, its fall to Earth is recorded thus -
"A ball of fire appeared in the Eastern sky and then it broke into two in an explosion resembling cannon fire. The two pieces trailed lines of fire across the sky and produced even stronger explosions on impact. This was the first record of eyewitness accounts about the fall of a meteorite on Earth in history, compiled at a time, when any possibility of such phenomena occurring was firmly denied. The report and the meteorite are both conserved at the Naturhistoriosches Museum Wien today. The Hrascina Meteorite bears inventory number "1" in one of the world's oldest meteorite collections, indicating that it started the collection".
A polished slab (weighing 0.56 grams) and a cast of the Hrascina Meteorite are on display at the Croatian National History Museum in Zagreb.
About the Lithothamnium Limestone:
Lithothamnium Limestone, called "Litavac", for short in Croatian, is a sedimentary rock.
This massive, porous type of limestone is mostly composed of red algae of the Lithothamnium order that inhabited the Paratethys Sea about 15.0 million years ago, in the Middle Miocene.
Although the limestone's name is derived from the algae, it also comtains the remains of Bivalves, Echinoderms, Bryozoans and Demersal forminifera.
Apart from the remains of sea organisms, Lithothmnium limestone contains fragments of Quartz and Calcite, Mica Flakes and fragments of rocks from the coastal area. This limestone was formed in the shallows of the Pannonian Sea, which surrounded Medvednica and other Pannonian Croatia mountains, which were islands at the time.
Along with Triassic Dolomites, Lithothmnium limestone forms a unique Karst zone on the West side of Mount Medvednica, which is home to the famous Veternica Cave - one of the longest in Croatia, with many canals measuring more than 7,000 metres in length, the Ponikve Karst field and other Karst forms in the areas of Horvatove stube and in the limestone sections of Lipa and Rog.
Lithothmnium limestone is one of the most commonly used in the construction of many of Zagreb city's buildings, the stone coming from nearby quarries.
Technical Details:
Stamps Issue Date: 22.10.2020
Designer: Dean Roksandic
Printer: d.o.o., Zagreb
Process: Offset
Colours: Multicolour
Stamp Sizes: 29.82 mm x 35.50 mm
Stamp values: 5.00 HRK (x 2 stamps)
An interesting post on Caves from other Postal Administrations:
2) The Caves of Meghalaya: A set of four postage Stamps issued by India Post on 15.08.2017
Links to some Interesting posts on Croatia on this Blog:
Vikram Bhatnagar has commented:
ReplyDelete"Study of rocks is called Petrology, seems to suggest a Sanskrit origin of the term, patthar se petrology? 🤔"
Apparently it is of Greek origin - "Petros" meaning "rock" and "logos" meaning "conditions of formation". Now for the interesting part - Greek and Latin are both derived from Sanskrit. Sanskrit is called as the mother language for the reason is that it is the oldest language that has given birth to almost all of the other languages (not just Indo-European). 😀😀😀
DeleteSantosh Khanna has commented:
ReplyDelete"GOOD information."
Thank you, Khanna sahab.
ReplyDeleteRajan Trikha has commented:
ReplyDelete"Very informative."
Thank you, Trikha sahab.
Delete