Diamond Films

(via ICA Lab Alert, No.10, September 1, 1987) Kurt Nassau writes:

Status
Much publicity both in the general press as well as in the trade has recently been focused on thin diamond films grown by a variety of low pressure techniques. Most of this publicity is highly exaggerated.

The facts are the following:
- Thin films of single crystal diamond can be grown on diamond, but the growth rate is so extremely slow that this is of no significance to the gemstone field.
- Thin films of polycrystalline diamond, composed of many tiny crystals, can be grown quite rapidly on a variety of surfaces, but adhesion is mostly very poor. Since such films are not single crystal, their presence should be easier to detect than most other coatings on gemstones. They could only fool a thermal diamond tester if the coating is very thick, when their presence should be immediately evident under the loupe.

Reference
More detail is given in an article being published in Jeweler’s Circular Keystone under the title “New Synthetics: Cause for Panic—or for the Blahs?”