Stretching along the central part of the Croatian Adriatic, are the Kornati islands. With their immense natural beauty, diverse coastlines, and preserved marine ecosystem, most of the Kornati islands were declared a National park in 1980. National park Kornati sizes about 220 km2 which consists of many islands, islets and reefs. National park Kornati was named after the biggest island in the group. This area is a specific geological phenomenon. Some of the past geological events in this area are strikingly reflected in the well-known Crowns of Kornati. The vertical cliffs of Kornati islands facing the open sea are the most popular phenomenon of this park. The Crowns are actually the surface of a large tectonic fault stretching from Istria and ending somewhere in Central Dalmatia (perhaps even further to the south), caused by the global movement of Africa to the north and its “crashing” into Europe. Vegetation on the islands is minimal, giving the islands a bald look, however, nature still thrives with plant life on the rocks. Crystal clear water, and uncover the all kinds of reefs, shellfish and many species of fish below the surface.
The Kornati islands were populated in prehistoric times; findings of stone hatchets at the bottom of the hill Pasinka on the islands of Kornati confirm the stated. The Kornati islands were a frequent target for invaders and thieves, from the Romans and the Venetians to the aristocracy from Zadar. Although today the Kornati islands are only populated during the summer months, old field and fishing houses spread out in secluded inlets on the Kornati islands, give away the presence of their owners. There is no electricity or fresh water springs on the islands.
The Kornati islands are a real heaven for yachtsmen, divers and all those who enjoy the solitude of untouched and the magnificence of nature. There are 20 restaurants on the Kornati islands which serve fish specialities. You can get to the Kornati islands by boat (if you own or you rent), or by organised boat excursions offered by tourist agencies. For more information you can visit the public bureau „Nacionalni Park Kornati “in Murter. The park is located about seven nautical miles from the island of Murter.
Karst topography is a landscape formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant rocks, such as quartzite, given the right conditions. Subterranean drainage may limit surface water, with few to no rivers or lakes. However, in regions where the dissolved bedrock is covered (perhaps by debris) or confined by one or more superimposed non-soluble rock strata, distinctive karst surface developments might be totally missing, the features occurring at subsurface levels.
Quartz is a mineral composed of silicon and oxygen atoms in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.
There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia.
Etymology
The word "quartz" is derived from the German word "Quarz" and its Middle hig German ancestor "twarc", which probably originated in Slavic, cf. Czech tvrdý ("hard"), Polish twardy ("hard"), Serbian and Croatian tvrd ("hard").
The Ancient Greeks referred to quartz as κρύσταλλος (krustallos) derived from the Ancient Greek κρύος (kruos) meaning "icy cold", because some philosophers (including Theophrastus) apparently believed the mineral to be a form of supercooled ice. Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz.
Crystal habit and structure
Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned, distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void; usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance within gypsum. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.
Formula:
SiO2
A variety of Quartz.
A smoky-gray, brown to black variety of quartz that owes its color to gamma irradiation and the presence of traces of aluminum built into its crystal lattice. The irradiation causes the aluminum Al(+3) atoms that replace Si(+4) in the lattice in a [AlO4]- group to transfer an electron to a neighboring monovalent cation (often Li+) and form a [AlO4/Metal0]0 color center. Quartz is the most common mineral found on the surface of the Earth. If pure, quartz forms colorless, transparent and very hard crystals with a glass-like luster. A significant component of many igneous, metamorphic and sedimentary rocks, this natural form of silicon dioxide is found in an impressive range of varieties and colours.
1. The more common macrocrystalline quartz is made of visible crystals or grains. Examples are rock crystals, the grains in sandstone, but also massive quartz that is made of large crystallites without any crystal faces, like vein quartz.
2. Microcrystalline quartz is made of dense and compact aggregates of microscopic quartz crystals and crystallites. Examples are agate and chert. The different types of cryptocrystalline quartz are colloquially subsumed under the term chalcedony, although that term has a more strict definition in scientific literature. It is worth mentioning that most chalcedony contains small amounts of another SiO2 polymorph, moganite, so it is not always pure quartz.
Occurrence
Quartz is a defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale. It is a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Quartz has the lowest potential for weathering in the Goldich dissolution series and consequently it is very common as a residual mineral in stream sediments and residual soils.
While the majority of quartz crystallizes from molten magma, much quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals like gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.
Well formed crystals of quartz collector values arise in cracks hydrothermal veins (as tzv.gangue) and a coating of natural cavities.
To get the log permission, please answer the following questions:
1. Walk away from a berth to the bay and find interesting geological phenomenon near water. It is possible to see something other than what is usual here.
2. What color is this geological phenomenon?
3. What geological phenomenon we can observe?
4. Is this geological formation macrocrystalline quartz or mikcrocrystalline quartz?
5. Estimate the size of this geological phenomenon - the width and height
6. Optional - submit a photo of you and your GPS near this geological formation.
Send your answers through my profile at geocaching.com (through e-mail or message center) and NOT in a log. You don't have to wait for me to approve your answers. Once you send your answers feel free to log this EarthCache as found. If there are problems with your answers, I will contact you.
U središnjem dijelu hrvatskog Jadrana proteže se jedinstveno kornatsko otocje. Zbog izuzetne prirodne ljepote, velike razvedenosti obale, ocuvane prirode te bogatog morskog ekosustava, godine 1980. veci dio Kornatskog otocja je proglašen nacionalnim parkom. Nacionalni park Kornati zauzima oko 220km2, a u okviru parka se nalazi iz moga otoka, otocica i hridi.
Vegetacija na otocima je vrlo oskudna. Ipak, priroda pobjeduje skromnim biljem na kamenjaru. Kristalno bistro more otkriva reljefno dno razlicitih oblika, crvene koralje, školjke i mnoge vrste riba.
Kornati su u prapovijesti bili naseljeni. O tome svjedoci nalaz kamene sjekire podno brda Padinka na otoku Kornatu. Kornati su cesto bili meta osvajaca i pljackaša, od Rimljana, Mlecana do zadarske gospode. Iako su danas Kornati nastanjeni samo ljeti, težacke i ribarske kucice, razasute po dobro zašticenim uvalama Kornata, odaju prisustvo njihovih vlasnika. Na Kornatima nema struje niti izvora vode.
Kornatsko otocje predstavlja pravi raj za nauticare, ronioce i sve one koji žele uživati u osami netaknute i velicanstvene prirode. Na Kornatima postoji oko 20 restorana sa ribljim specijalitetima. U nacionalni park se može doci brodom (vlastitim ili iznajmljenim) ili u organizaciji turistickih agencija koje organiziraju izlete. Detaljnije informacije mogu se dobiti u prostorijama Javne ustanove „Nacionalni park Kornati“ u Murteru. NP se nalazi na udaljenosti oko sedam morskih milja od Murtera.
Krški reljef je krajobraz formiran od topivih stijena kao što su vapnenac, dolomit ili gips. Takav reljef karakterizira podzemni sistem sa jamama i špiljama. Zabilježeno je i da pod pravim uvjetima više trošno otpornih stijena, kao što je kvarcit.
Kremen (njem. Quartz; ili kvarc) je polimorfna modifikacija (kristalni oblik) silicijeva dioksida (SiO2) i jedan je od najrasprostranjenijih minerala u prirodi.
varca se sastoji od okvira silicija i kisika tetraedara SiO4, sa svakim silicijem dijeli dva kisika pa daje ukupnu formulu SiO2. Kvarc je drugi po redu najzastupljeniji mineral koji se pojavljuje u Zemljinoj kori odmah nakon feldspalta.
Postoji mnogo različitih vrsta kvarca, od kojih su neki poludrago kamenje. Od davnina razne vrste kvarca najčešće su korišteni mineral u izradi nakita i rezbarija od kamenih rezbarija i to posebno u Euroaziji.
Etimologija
Riječ "kvarc" je izvedena iz njemačke riječi " quarz", koja je vezana sa riječi "twarc" iz srednjovjekovnog njemačkog jezika. Ova riječ vodi vjerojatno originalno porijeklo iz slavenskih jezika češki tvrdý ("tvrd"), poljski twardy ("tvrd"), hrvatski tvrd.
Kod starih grka navode kvarc kao κρύσταλλος (krustallos) izvedena iz stare Grčke κρύος (kruos) što znači „ledeno hladna”, pošto su neki filozofi (uključujući Teofrast) očito vjerovali da je mineral nastao od super hladnog leda. Danas se pojam gorski kristal ponekad koristi kao alternativni naziv za najčišći oblik kvarca.
Kristalni oblik i struktura
Kvarc pripada trigonalnom kristalnom sustavu. U kristalima se pojavljuje u obliku heksagonske prizme koja završava piramidom, zapravo kombinacijom pozitivnog i negativnoga romboedra. U prirodi kvarcni kristali su često dvostruki, iskrivljeni, i tako srasli sa susjednim kristalima kvarca ili drugih minerala, tako da pokazuju samo dio svog oblika, ili svi zajedno nemaju očito kristalno „lice“ već se pojavljuju masivno. Dobro formirani kristal uglavnom je u obliku „kreveta“ i raste slobodno u prazninu. Obično su kristali spojeni na drugom kraju u „matrix“ i samo je prisutan jedan završetak piramide. Kvarcna geoda je takva situacija gdje je praznina kuglastog oblika obrubljena ležištem kristala koji su usmjereni prema unutra.
Podjela kvarca
Kvarc je najčešći mineral koji se nalazi na površini Zemlje. Čisti kvarcni oblik je proziran i vrlo teški kristal čistog sjaja. Taj prirodni oblik silicij dioksida nalazimo u impresivnom rasponu raznih vrsta i boja. Kvarc može biti od dimno-sivog, smeđeg do crnog, boju dobiju od gama zračenja i prisustva tragova aluminija koji su ugrađeni u kristalnoj rešetci.
1. Veliki kristal kvarca: koji je češći sastoji se od vidljivih kristala i zrna. Primjeri su kameni kristali, zrna u pješčenjaku, kao i masivni kvarc koji se sastoji od velikih kristala bez kristalnih ravnina poput žile kvarca.
2. Mikrokristalni kvarc je izrađen od guste i kompaktne nakupine mikroskopskog kvarcnog kristala i kristalića. Primjer su ahat i rožnjak. Različite vrste kripto kristalnog kvarca kolokvijalno su smještene pod pojam kalcedona, iako taj pojam ima više strogu definiciju u znanstvenoj literaturi. Vrijedno je napomenuti da većina kalcedona sadrži male količine drugog SiO2 polimorfa, moganite, tako da nije uvijek čisti kvarc.
Način postanka
Kvarc je osnovni sastojak granita i magmatskih stijena. Te je vrlo uobičajen u sedimentnim stijenama, kao što su pješčenjak i škriljevac. Također je često sastavni dio škriljevca, gnajsa, kvarcita i drugih metamorfnih stijena. Kvarc ima najmanju mogućnost trošenja zato ga često nalazimo kao zaostali mineral i sedimentnim tokovima. Iako je većina kvarca iz rastaljene magme, dio kvarca se kemijski taloži iz vrućih hidrotermalnih žilama uz minerale ruda kao zlato, srebro ili bakar. Veliki kristali kvarca se nalaze u pegmatitu. Dobro formirani kristali mogu dostići do nekoliko metara u dužinu i težiti nekoliko stotina kilograma.
Dobro formirani kvarcni kristali kolekcionarske vrijednosti prvenstveno nastaje u pukotinama hidrotermalnih vena (kao tzv.gangue) i kao obloga prirodnih šupljina.
Da biste mogli logirat molim da odgovorite na sljedeća pitanja:
1. Prošećite od veza do uvale i nađite zanimljive geološke fenomene u blizini vode. Vidjet ćete nešto drugačije od uobičajenog.
2. Koje je boje geološki fenomen?
3. Koji geološki fenomen možemo istražiti?
4. Je li ovo geološka formacija velikih kristala kvarca ili mikcrocrystalline kvarc?
5. Procijenite veličinu ovog geološkog fenomena – visinu i širinu.
6. Ako želite možete staviti fotografiju vas ili vašeg gps uređaja blizu mjesta ovog geološkog fenomena.
Pošaljite svoje odgovore putem mog profila na geocaching.com (putem e-maila ili message centra), a NE putem loga. Ne morate čekat da odobrim odgovore. Kad ste poslali odgovore možete slobodno logirat ovaj earthcache. Ako bude problema oko vaših odgovora kontaktirat ću vas.
Thanx to vontere to Croatian translation.
Můžete poslat odpovědi i v češtině :-)
https://en.wikipedia.org/wiki/Quartz
http://www.quartzpage.de/gen_rock.html
http://www.quartzpage.de/gen_form.html
https://www.mindat.org/min-3689.html