December 24th

The last door opens today and we hope you had a great time with our calendar. 

If you can no longer recognise a stone, you can check which stone goes with which note here >>>>

 If you would like one or more pieces to be larger, simply write to us. 

Of course, we are always happy to receive feedback so that we can continue to optimise the calendars. Please let us know what you liked, what you didn't like and what you would still like to see. Haasler (at) krantz-online.de or simply leave a rating for the product.

Now we wish you

MERRY CHRISTMAS

December 17th

Today's pyrite (iron sulphide) is a fascinating stone. Crystallizing in the cubic crystal system, it can form many shapes: Cubes, octahedrons, pentagon-dodecahedrons and combinations of cubes and octahedrons as well as pentagon-dodecahedrons and cubes are possible. Also particularly fascinating: pyrite suns.

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Pyrite suns are formed in sedimentary areas, mainly in coal or clay shale deposits. Due to the weight of the sediments, the pyrite crystals cannot crystallize as cubes and are virtually forced to grow flat or sideways.

Sometimes there are minerals which share the same chemical composition, but have very different crystal structures. We call them polymorphs. The different crystal structures can lead to completely different physical properties: e.g. graphite and diamond (both consisting of pure carbon, but diamonds have a hardness of 10 while graphite has a hardness of 1), or here again: Pyrite and marcasite. Both minerals consist of iron sulphide. Marcasite is significantly more unstable.

Marcasite is good for producing sparks, which was already used by Neanderthals. How is shown on Instagram & Facebook in a small video.

What distinguishes pyrite from gold? Because of its high iron content, pyrite sticks to a magnet, which gold does not.

We hope you enjoyed the advent calendar so far and welcome your feedback via e-mail, or by rating the product in our own webshop or on Amazon!

Where do you put all your new treasures?  ?

We will show you some options:

December 12th

Hardness of stones and minerals is measured on the so-called Mohs scale. Friedrich Mohs was a german-austrian geologist who established these units in his work 'Grundriss der Mineralogie' (engl. title 'Outline of Mineralogy'), published in 1822.

Softer stones, such as today's talc or yesterday's biotite, can be scratched with a fingernail (see our video on Instagram).
Hardness 3 (calcite from December 5) can be scratched by a copper coin, hardness 4 (aragonite from December 6 or the stone found on the 15th) will be scratched by a steel knife. For higher degrees of hardness, the material in question must be scratched with the corresponding stone, e.g. quartz can scratch softer stones such as agate or calcite, but not harder stones such as topaz (hardness 8) or corundum (hardness 9). For such a scratch test, you can purchase the hardness scale with its typical specimens in our shop.

December 7th

Jasper has many varieties, a small selection can be seen here:

December 6th

You've now learned about a number of carbonates: dolomite, calcite and aragonite. They all contain the chemical symbol CaCO₃ which stands for calcium carbonate.

A carbonate is a poorly soluble salt. Together with carbon dioxide, they play a key role in the development of life on earth.  

They were also 'involved' in the formation of skeletons, shells as well as other solid organic parts. In some groups of organisms, calcium carbonate skeletons are composed of aragonite, in others of calcite. This is due to the marine chemistry at the time when skeletal elements evolved in the group of organisms. Calcite is predominantly formed at low magnesium concentrations, while the formation of calcite is inhibited at higher concentrations.

Because of its high magnesium content, nowadays dolomite is in demand for fertilizers, food supplements and cleaning agents.

December 2nd