The word tyelpetéma in tengwar of the Quenya mode2. The first character, equivalent to 'tyë', is a palatal of the tyelpetéma series.
One of the témar or sound-series of the tengwar as used to represent the sounds of the Quenya language.
The tyelpetéma appears to have been unique; while each of the other four series consisted of a set of six individual 'letters', the palatal sounds of the tyelpetéma were formed by adding a mark of two dots beneath another character, as in the example above3. This is the equivalent of adding a 'y' after the letter in English to form a single distinct consonant sound. To use Tolkien's own example from Appendix E to The Lord of the Rings, the sound 'ty' here has the same sound as the initial consonant in the (British pronunciation of) the English word 'tune' - something close to, but distinct from, 'ch'.
The choice of the Quenya word for 'silver', tyelpë, is for purely phonetic reasons: it happens to start with a palatal sound, 'ty', that belongs to this series.
Replicating a specific 'mode' of tengwar is extremely difficult, and this transcription is necessarily approximate. The difficulties are particularly acute in this case because examples of 'true' Quenya are extremely rare: most of Tolkien's transcriptions to tengwar are from Sindarin, English or, in the unique case of the Ring inscription, the Black Speech.
In fact Tolkien tells us that this was the 'usual' method of marking a palatised sound, not the only means of doing so. We are given no hint, though, as to what other methods may have been used. (The Lord of the Rings, Appendix E (i), The Fëanorian Letters).