Colloids and Quartz Crystals

It is a basic idea of present-day geology that quartz crystals, like many other mineral crystals, have originated in hot, mineral-containing vein water over thousands of years.  Certain quartz crystals nevertheless show features which point to an original colloidal-gelatenous silica material.  One can consider the following three well-known special types of quartz crystals:

Rutile quarz

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Turmaline quarz
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Phantom quarz
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The gold-yellow rutile needles contained in the quartz crystals in the first two pictures are folded like bundles of hair.  In the fourth picture tiny broken rutile pieces float free inside the quartz crystal material.  Pictures five and six show black tourmaline needles, the finest and thinnest of which have been bent in varying directions like hairs in a transparent cream.  With a hydrothermal crystallization from the center out, the needles, bundles and fragments would have had to grow at the same time as the quartz, or else in some remarkable way have grown through an already-formed crystalline quartz material.  Is that probable?

If the crystallization of the quartz taken place in a colloidal-gelatenous silicious material, on the other hand, the phenomena would be easier to explain: the needles and needle-bundles would have formed themselves inside the soft silicious mass by extracting their corresponding elements.  In the case of the thin broken rutile pieces in the fourth picture, these would have broken off from rutile-stars (see picture 3) and remained stuck in the silicious gel.  Later the quartz would have crystallized as an entirety.

A similar question is posed by the phantom quartz crystal.  At first glance one can think of a completely hydrothermal explanation:  the inner crystal has a green surface from a short period of layering by chlorite, carried for a short time by hydrothermal solution.  Afterwards the growth continued without coloring, in that the hot silica solution became clear again.

Still, the milky-cloudy quality of the green phantom surface is irritating.  Because of the projecting chlorite fragments and the inclusion of small gas bubbles the impression is awakened of an irregular layering in a soft material.  One could say, perhaps, that the irregularities are the result of a longer duration of the period of chlorite layering.  Still, the small chlorite fragments and the gas bubbles seem to contradict this explanation.

How could the process have taken place in a colloidal silica mass, however?  The inner crystal could have formed itself within a thick, colloidal silica gel in a first period.  Then chlorite particles and gas bubbles could have layered on the surface of the crystal, still surrounded by silica gel, and later enclosed by the outer form.

It would be perhaps conceivable that both types of origin took place:  At one location growing "atomistically" in silica-rich hot water, and at another place by a stepwise crystallization out of a colloidal-gelatenous silicious mass, possibly with transitions between the two extremes.