From TactWiki

Overview

Facets are uncut gems that are received as the rewards of completing Diplomacy Writs. Most Writs have as a reward a choice of a particular kind of Facet or a choice of one of two kinds of Facets. Some Facets are only available from writs in one particular Diplomatic Prestige Center, where others are available in several. Consult with the Writ list and look at the rewards to determine where to go to do a Writ that rewards you with the type of Facet you are seeking.

Having a Gem Cut

Facets are taken to a Lamplighter Lapidarian and handed in to be cut into Gems. When a Lapidarian cuts a Gem for a player a Glyptic Dust from the players pack as well as the Facet to be cut will be used up. Make sure and purchase Glyptic Dust from the Lapidarian before you request having a Facet Cut.

When turning in Facets to a Lapidarian typically a rare Gem is the result. Other possibilities are that you may receive a "Supergem", which is a Ultra-Rare heroic version of the cut gem, or a Dweomerstone. The Dweomerstone is basically junk, a failed attempt to cut the Facet into a Gem, that sells to any vendor for a small amount of coin. Developers have noted that the chances for getting a Dweomerstone is at 5% of turn-ins. "Supergems" seem to a have a drop rate of 5-10%.

After the Lapidarian cuts a players Facets the resulting Gems are then used to assemble Diplomacy Masks.

Lapidarians

Lamplighter Lapidarians are found in the Capital cities of each continent. Nearby each Lapidarian is a Mask Assembly Station.

Lapidarians are also merchants who sell Glyptic Dust and Socketed Diplomacy Masks.

Facet and Gem Correlation

There are a wide variety of Diplomacy Masks that can be assembled using Gems but a mask with a single common Gem in it will have a certain effect depending on the type of Gem used. The effect is either to add one point of expression to the parley depending on the type of Gem, to alter the Parley Indicator in favor or either the Player or the NPC, or to add or subtract from the refresh timers on all of the Player's and/or NPC's cards. The effect is doubled by using two of the same type of Gem in a Mask.

Masks using two different gems will contain the effects of both of the gems used.

When constructing Masks using three of the same type of Gem the effects change though according to the second chart listed below.

For common gems, each affect will apply by 1 point for each gem included in the mask, except that a mask with 3 of the same type of gem has different effects as follows: