TUMBLE-POLISHED BAROQUES AND CABOCHONS
Large quantities of irregularly-shaped gems, known as baroques or tumbled gems, are now prepared very cheaply by tumbling pieces of rough in barrels along with suitable abrasives and liquids, and later, with polishing agents. The process takes many days or even weeks, depending on the kind of material, the size of the barrels, and other variables which are carefully considered by the manufacturers.
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CHECKING POSITION OF OPTICAL EFFECTS
To determine the strength, perfection,  and  position  of any  special optical effect, stand beneath a single pinpoint source of light, e.g., a single electric bulb (not a fluorescent light) or the sun. Diffuse light, such as that found out-of-doors on a cloudy day, results in broad, diffuse reflections which are more confusing than revealing.

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ADDITIONAL NOTES ON STAR AND CATSEYE GEMS, MOONSTONES, ETC.
As previously explained, star- and catseye-causing inclusions, and those responsible for moonstone, sunstone, and other sheen or color effects, occur in certain planes in the host crystal. It is up to the cutter to examine the rough to determine how he can best cut it to place the special effect squarely on top where it belongs.

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PROPORTIONS OF CABOCHONS
The proportions of cabochon gems vary widely, some being quite thin in relation to their width, others being quite thick. Gemstones displaying star, catseye, and moonstone effects must be cut reasonably thick to “sharpen” the lines of light in the case of the first two and to induce strong sheen in the case of the last. Good star and eye effects require that the thickness of the cabochon be from i/3 to i/2 the width; good moonstoone effects are seen with the same proportions but do not lessen greatly until the thickness is reduced to about l/8 the width, depending on how strong the effect is in the rough used. Catseye gems, particularly chrysoberyl catseyes, often are cut with high tops and sharp curvatures at the crests, somewhat elongated along the streak of light, if the stone is elliptical.
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CABOCHON GEMS
Because cabochons are entirely hand-shaped, the final curved surfaces depend for their geometrical perfection upon the skill of the lapidary. The ideal cabochon should be symmetrical in profile and outline, both of which can be easily determined by visual inspection.
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SURFACE FINISHES
Maximum brilliancy in any faceted gem is achieved only when the facets are cut as fiat as possible and polished to the highest degree of smoothness. The quality of surface finish is highly important in cabochon gems also, particularly in those displaying special optical effects such as star stones, cats eyes, and moonstones. A perfect polish also greatly enhances the play of color in opal.
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CULET FACET
. There is no question that this facet destroys the ability of a small area near the tip to properly reflect light, yet, through long-standing tradition, this culet is still placed on brilliant
cut gems.

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NATURALS
If one examines a parcel of round diamond brilliants, he is sure to see, sooner or later, a peculiarity which is confined only to the diamond. This is the existence of small flat spots along the girdle, called naturals, which glisten brightly in marked contrast to the dull surface of the rest of the girdle. There may be one or, at the most, four such spots evenly spaced around the periphery. They are remnants of the natural faces of the diamond crystal, in this case, the octahedron. They result when the cutter grinds a section of the crystal into a circular outline, part of which is to become the girdle of the finished gem.

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THE GIRDLE AS AN INDICATOR OF QUALITY
By examining the accuracy with which the facets of the crown meet the facets of the pavilion along the girdle, even the inexperienced person is able to judge the relative skill of the lapidary. It goes without saying that the skilled workman will pay equal attention to all parts of the gem and not just to those which are most obvious.

Offset or mismatched facets are shown in Figure 20 along with other cutting errors that can be easily detected with the naked eye or under low magnification. Such defects are seldom glaring but they depart from the ideal and are silent signs that the basic material of the gem was not considered worthy of the best cutting skill, or that the lapidary was sloppy in his work. It is almost an invariable rule in the lapidary arts that the finest materials are sent to the finest cutters for treatment. Only by doing this will it be possible to realize the fullest potential value of the rough. Thus, every indication of poor cutting should make the buyer suspicious of quality, and, of course, of real value. This rule is rigidly applied to the most expensive rough and relaxes as the rough becomes cheaper, until the most slapdash lapidary work generally appears upon gems cut from the poorest rough.

GIRDLES
The thin band which separates the crown, or top of the gem, from the pavilion, or bottom, is know as the girdle. It may or may not be polished, or covered with very small facets. A girdle which is too thin is likely to chip when the jeweler sets it in jewelry, as shown in Figure 19.

If the girdle is too thick, it results in a clumsy-looking gem. The proper girdle is neither too thin nor too thick, combining graceful thinness with ade¬quate thickness to resist the stresses applied to it when seized by the prongs which secure the gem to its mounting.
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