Crystal patterns

There are substances that are called isomorphic: they crystallize in the same way, despite the different composition. Crystals of one such substance are able to grow in a saturated solution of another: it turns out, as it were, a "crystal in a crystal". If you cut it, then a geometric pattern will appear on the cut.

Crystals of one such substance are able to grow in a saturated solution of another: it turns out, as it were, a crystal in a crystal. If you cut it, then a geometric pattern will appear on the cut

The most accessible among isomorphic substances are alums, crystalline hydrates of double sulfates with the general formula M'M"'(SO4)2*12H2O. Let's use their three varieties: dark purple chromopotassium KCr(SO4)2*12H2O, green ammonium iron NH4Fe(SO4)2*12H2O and colorless aluminum-potassium КАl(SO4)2*12Н2О.

Pour water into an enameled or glass dish, add some alum (one type) and heat, stirring with a glass or wooden stick, but not to a boil. When the salt dissolves, add another portion of the same alum and heat again. When the solution becomes saturated, quickly filter it through a cotton swab placed in a glass or enamel funnel rinsed with boiling water. If the funnel is cold, premature crystallization may begin and the crystals will clog the funnel.

Cover the jar with the alum solution and let it cool slowly. Small crystals will fall to the bottom. If they grow together, heat the solution by adding a little water and cool again. Remove the crystals, dry, transfer to a test tube and close it with a stopper. Also prepare a crystal of other alum. Save saturated solutions! Label the jars to avoid confusion.

Select one crystal of each type, tie it with thin threads (for example, from a nylon stocking) and lower each into "your" solution. Keep jars away from drafts; cover them with paper covers.

In about a week, the crystals will noticeably grow. Swap them. If from the very beginning two crystals are hung in each jar, then there will be even more alternations of colors. In order not to get confused, attach labels to the ends of the threads and write down in the laboratory journal how long and in what solution the crystals are.

A regular alum crystal is shaped like an octahedron, but we don't need a perfect crystal. On the contrary, the more bizarre the shape, the more interesting the pattern on the cut. At the same time, you can grow crystalline intergrowths - druze, taking already fused crystals for seeding. If they start branching while growing, don't fix them; what's more, you can control the growth of the faces yourself. Lubricate the edge with Vaseline and it will stop growing, wash off the Vaseline with acetone and the edge will grow again.

Cut the finished crystal with a wet, harsh thread; this job requires precision and patience. Smooth the cut surface with sandpaper and polish on wet Whatman paper in a circular motion.

Depending on how the cut plane is chosen, how many layers are in the crystal and what is their thickness, a wide variety of geometric patterns will be obtained. Friends have more options. Immediately cover the cut crystal with a pattern with colorless varnish (nail polish is suitable), otherwise it will fade and crumble into powder.

It is much easier to make a pattern from ammonia-ammonium chloride crystals. True, it is colorless, but it reminds me of a pattern... However, let's not get ahead of ourselves.

Pour ammonium chloride into warm water and mix thoroughly to prepare a saturated solution. Take a glass plate or a mirror, wash the surface, apply the prepared solution to it with a brush. Let the plate with the solution cool slowly in the air, and so that dust does not get on it, you can hide it in a cabinet. After a few hours, the water will evaporate and a pattern will form on the glass. You don't even have to peer to understand what it reminds you of: a frosty pattern on a winter window.

Such an experience, of course, is best put before the New Year. Heat does not threaten the artificial frosty pattern, but it must be kept away from water...