Here you can see some samples of my numerous own finds...
Birthing Stones (Biotite Lenses)
"Pedra parideira" - birthing stone - so call the Portuguese the remarkable Biotite Lenses found in a rocky mountain range in northern Portugal. They are a metamorphic mica concretion with a feldspar core. They have only been found in this one few acre areas in Portugal. The bed rock, ca... 300 million year-old granite was metamorphosed by the pressure and heat of movements in the earth´s crust. Thus, the Biotite Lenses occur in an exactly northeast-southwest direction. Just as strange as the virtual existence of the Birthing Stones, is the phenomenon that one can observe at the site on hot days in July after the summer solstice and on frost sparkling January days after the winter solstice. The Biotite Lenses really are birthed. The locals say that it crackles and pops in the rock and the black lenses come to light. Thereby, they cleave away at times whole plates of ton-heavy granite. But this birthing process occurs only during very hot or cold spells. Normally, the "Pedras Parideiras" slumber peacefully in Mother Earth. The native people, progeny of the Celts, as their blue eyes and blond hair attest, guard the Biotite Lenses as a treasure. No house in the region is without at least one lens in the window sill. They bring the people fertility, luck, energy, and protect against evil spirits - no wonder, when the "parideiras" even overwhelm the granite.
Due to the uniqueness of the Biotite Lenses, in 2007 a geological park was established in the area. All Birthing Stones that are offered were found before the year 1990.
Spanish Olivine (Ojenite)
Ocurrences, geology: the singular about this stone that only occurs in southern Spain are his distinctive colors and structures.These olivines virtually always have a dark-green until black eye in the middle, surrounded usually from an olive aura. Outside numerous brown and beige wave lines follow, which show a fantastic scene and figures. The like rings of a tree appearing drawings of the Spanish Olivins document changes between moist and dry periods of the southern Spanish climate, to which the stone was exposed since its formation. Mineralogical analyses yielded, that it is a 350 million year old, fine-crystalline peridotite, that has intruded during the formation of the mountains in Andalusia from 80 kilometers of depth. Olivine crystallizes rhombic, its hardness amounts to 6,5 - 6,75, the density lies with 3,34
In the year 1989 I encountered for the first time this strange stone, whe I was on a mineral collecting trip in southern Spain. I discovered two small quarries in a contact zone between ultrabasites and sedimentary rocks. Some few samples of this material were taken to the geological department of the University of Freiburg and then analysed. The thin section displayed a fantastic array of green colours and I was really surprised to confirm a content over 90% of olivine.
The Spanish Olivine has been manufactured from skilled gemstone cutters with a lot of feeling and intuition for this rare and unique stone.
Glaucophane with Garnet and Omphacite
The singularity of this stone that can be found only in the Alps is the beautiful colour contrast in combination with wave patterns, formed during the high grade metamorphism under extremely high pressure of 8000-10000 bar and temperatures of 300-400 degrees. Thereby the crystals were arranged in parallel wave structures. Mineralogical analyses have shown that the material is 35-40 million years’ old, crystalline Glaucophane Schist rising up from great depth during the folding of the Alps. Glaukophane crystals are monocline, the hardness is between 5 - 6, the density ranging between 3 and 3,2.
I have found the Hornblende Diorite in the south of Finland in glacial debris. The rock consists of large oval hornblende crystals in a quartz-feldspar-matrix. Where the stone really originates from is totally unknown. Similar occurrences from other areas apparently don´t exist.
Pyrite with Magnetite and Hematite
These wonderful ores originate from Northern Italy, they contain various metals and therefore they show a great variety of structures. Each ore mineral has an own specific luster, producing a special pattern in these stones. Picking up one of them, you´ll notice immediately the higher weight caused by a larger iron content.
The Amethyst Chalcedony originates from northern France and is composed mainly by a hydrothermal mineral deposit, containing amethyst with agate and chalcedony, occasionally with pseudomorphism after barite. The amethyst bands have a surprisingly intensive colour, red hematite inclusions cause a larger variety of patterns.
The Cornaline Jasper originates from northern Italy. In the area I remarked that in various walls of the local buildings intensive red stones with white veins were used as construction material. When I was making a trip with my mountain bike suddenly I found a small outcrop of this stone and brought some of them home. A conspicuous organic pattern sometimes remembers petrified wood.
Hematite in Rhyolite
This stone from the North of France has experienced quite a bit! The red-brown matrix is a rhyolite that has come to the surface by several volcanic eruptions. Subsequently the area where the lava flowed out, has undergone intensive tectonic movements, which broke up the rock along fractures. Angular fragments in this breccia are witnesses of this event. Circulating waters, intruding thereafter into these cracks, have formed numerous small sparkling hematite crystals, giving the stone a magic gleam. The remaining cavities were filled with quartz crystals in the course of the millenniums. These stones can tell quite a lot...