Artificer's Lore

Some materials, gemstones and metals have particular affinities for certain magical elements. Use of correct material can expedite crafting time, slightly enhance the potency of an item, or otherwise increase its effectiveness. Likewise, using inappropriate materials can make the artificer’s job more labourious, or less fruitful. The connection between material affinities and benefits has proven impossible to pin down with any precision, but it exists nonetheless.*
*DM's note: The perk from using "better" materials will usually be: 1 week less crafting time, an extra charge or two, +1 to the item's DC, but the DM will decide this on an item-by-item basis, in some fruitless attempt to maintain balance.

Materials

Adamantine. Potency nil. Penalty all items with magical effects. Armor and weapons made from adamantine have additional properties. Natural adamantine is found exclusively in Melorn, deep within Mount Pelithyr. Some transmuters have proven capable of recreating adamantine with magic.
*NEW* Brass. Potency: all items with magical effects. Penalty: any armor or weapons. Brass armaments require additional enchantments to make durable enough for combat, and thus typically take somewhat longer to craft.
Bronze. Potency: items dealing lightning damage. Penalty: items dealing fire damage.
Demonsteel.
*NEW* Glassteel. Potency and Penalty: spells or effects that deal thunder damage. Glassteel does not form naturally, but is commonly created by transmuters and alchemists in Haven and Hollyhock. A character with knowledge of glassteel and its properties, and who has at least one 3rd level spell slot, can create glassteel items during downtime. Glassteel is immune to corrosion and is a material of choice for ooze-hunters, whose caustic acid degrades most weaponry.
Ironwood. Potency: magic from the druid spell list, excepting those that deal fire or lightning damage. Penalty: spells or effects that deal fire or lightning damage. Ironwood is difficult to harvest, and relatively rare except in the Arborean province of Melorn, where the elven druids make common use of Ironwood for armaments.
Mithril. Potency nil, penalty nil. Mithril armor and weapons have additional properties.
Shadowstuff.
Silver & Truesilver. Potency: radiant or holy magic. Penalty: necrotic and unholy magic. It is uncommon for magical properties of silver weapons to be accessible to evil-aligned creatures. Truesilver is an especially potent variant of silver, found exclusively in the Plane of Air and Sanctuary.
*NEW* Wishsilver. Potency unknown but of great power, penalty unknown. Among the rarest metals in existence, Wishsilver (also known as Genie's Gold) is a collective term for the metal and jewelry worn by a genie upon their ascension from their mortal lives into Djinnhood. Only the metal worn at the genie's time of ascension is blessed in this way, and the genie cannot create more, even by means of a Wish spell. Moreover, a genie's wishsilver vanishes upon their death, except that which was given willingly by the genie and without magical coercion. This metal is exceedingly rare, and its properties have yet to be studied. Sage's lore suggests any item crafted of this legendary metal would be of unparalleled quality.

Gemstones

*NEW* Agate. Potency: Spells that call on the power of voice (e.g. Dissonant Whispers, Command). Penalty: none.
Agate, Fire. Potency: any fire magic. Penalty: any water or cold magic.
Amethyst.
Jasper.
Aquamarine. Potency: any item created or wielded by women, and water magic. Penalty: any item created or wielded by men, and fire magic.
Diamonds. Potency: necromancy, astral projection, healing. Penalty nil.
Tigerseye. Potency: strength-based enchantments, and divine magic associated with Ko'suth. Penalty: intelligence-based enchantments.
*NEW* Topaz. Potency fire, and the Enemies Abound spell. Penalty nil.
Onyx. Fortifying spells or defensive buff-type spells (e.g. Stoneskin). Penalty: damaging spells.
Emerald. Potency: Poison or acid-type spells, and Enchantment magic. Penalty: Conjuration and wind magic.
Sapphire. Potency. Conjuration, especially of water elementals or sea creatures. Penalty: Evocation magic.
Moonstone. Transmutation and spells on the druid spell list. Penalty: spells on the warlock spell list, and spells that deal radiant damage.
Ruby. Potency: Abjuration (protection) magic against evil. Penalty: offensive magic.
Jade.

Enhanced Materials

Some items can be, or must be, enhanced to serve greater purpose in magic artificing. This is an area of active and intensive study. The most common of these enhanced materirals are "annual" items; items that have been specially aged for precisely a year and a day. Most legendary items require an "annual" component.
Aged Stone Giant's Heart (Annual).
*NEW* Elemental Heartstone (Annual). These gemstones are empowered by raw elemental magic. Creating a heartstone requires giving a specific gemstone to an elemental and allowing the stone to grow and age within the elemental's primal form for one year. These elementals form and reform regularly in nature, so this aging process requires a craftsman to either summon the same elemental each day for a year (by virtue of a Bowl of Water Elementals or a Conjure Elemental Spell), or to bind a wild elemental (e.g. with Planar Binding).
The type of gemstone required varies by elemental; amethyst for earth elementals, aquamarine for water elementals, fire agates for fire elementals and quartz for air elementals. An amethyst aged in this way is considered to be from a CR 19 monster for the purposes of crafting magic items.
Brined Basilisk's Eye.
Brined Nothic's Eye.
Charred Efreeti Knucklebones.
Cured Dire Bat Hide.
Death Tyrant Skull.
Druagar Binding Nails.
Fermented Elfsblood.
Psychic Brine.
Royal Water.
Vampyr's Bane.

Magic Item Recipes

The following is a list of known crafting components useful for replicating specific magic items.
Flametongue Weapon. A weapon quenched in magical heat during the forging process, be that a mote or primal fire from a Fire Elemental, the fireblood of a Remorhaz worm, or the searing breath of a dragon willing to aid the smith. The result is a weapon ablaze with fire and power.
Bloodwell Vial.
Hide of the Manticore.
Ring of Regeneration. Simply fashioned from any precious metal and a fine gemstone etched with arcane glyphs and soaked in the blood of powerful regenerating creatures--namely the heart's blood harvested from a vampire, or alternatively from a hydra--although for peculiar reasons, only hydras allowed to grow at least nine heads are useful for this particular item. For this, and most crafting purposes, only the blood contained by the heart at the creature's death is of any use.
Knives of the Deathless.
Cloak of the Bat.
*NEW* Circlet of Blasting. Simply fashioned from metal, fitted with fire agates and imbued with elemental fire, this circlet allows the wearer to cast Scorching Ray once per day. Traditionally made with a mote of primal fire collected from a wild fire elemental (CR 5), wealthier craftsman have forgone the mote of fire in place of fire agates or topazes worth at least 1,000 gp, eliminating the need for hunting elementals.
*NEW* Elemental Gem (Fire). A single-use gemstone containing a bound fire elemental. The most common component is a mote of fire from a wild fire elemental (CR 5). If the craftsman (or their assistant) is capable of casting Conjure Elementals, then the component is unnecessary.
*NEW* Staff of Fire. Those who wield the staff of fire drown their enemies in agony and immolation. These staves are as rare as they are valuable, owing in part to the difficulty in their construction--these staves are exclusively crafted from the heart of a phoenix (CR 16), rare in the plane of fire and virtually unheard of in the material plane, save perhaps by those followers of Azrael.