Here's the updated list of herbs and crystals mentioned so far:
Acorus calamus
Amber (x2)
Alexandrite
Amazonite
Amethyst
Andalusite
Apatite Cat's Eye
Arsenic
Artemis Herb
Asafoetida
Avena sativa
Bamboo
Ban Xia
Basil
Bergamot
Borage
Carnelian
Chamomile
Chrysanthemum
Chrysoberyl
Cubeb
Damiana
Dandelion
Demantoid Garnet
Diamond
Digitalis
Dill
Diopside
Dolomite
Drusey Quartz
Dumortierite
Eagle Eye Agate
Echinicea (x2)
Echsholzia
Eilat Stone
Elder
Elderberry
Elecampane
Elecampane Root
Elfwort
Emerald (x2)
English Cowslip
Ephedra (x2)
Epidote
Eucalyptus (x2)
Euclase
Eudialyte
Euphrasia
European Alder
Eyebright
Fayruz
Fennel
Fenugreek
Frankincense
Gagroot
Galena
Garlic
Garnet
Ginger
Ginseng
Gold
Groundsel
Guava
Gug
Gypsum
Haematite
Hashish
Heliotrope
Houndstongue
Hyssop
Illicium verum
Indian Paint Brush
Indicolite
Inula conyza
Iron
Kelp
Kif
Kinnickkinnick
Korean Ginseng
Kudzu
Kyanite
Labradorite (x2)
Lamb's Quarters
Lapis Lazuli
Lapis Linguis
Larkspur
Lavender
Lepidolite
Lespedeza
Lion's Tooth
Lodestone
Loosetrife
Lotus
Luffa
Ma Huang
Mandarin
Mandrake
Marjoram
Marshmallow
Mica
Moonstone
Motherwort
Narcissis
Nasturtium
Neckweede
Nelka
Nepeta cataria
Nephrite (x2)
Neroli
Nettles
Nightshade
Niobium
Noni
Nonu
Nutmeg (x4)
Oak
Olive
Onyx
Opal
Oregano
Oryza sativa
Padparadschah
Pearl
Pepper
Peridot
Prickly Broom
Raspberryspar
Rattleweed
Rauwolfia
Red Clover
Red Coral
Rhodochrosite
Rhododendron
Rhodonite
Rhubarb
Rose Quartz
Rosemary
Rubellite
Ruby
Rue
Safflower
Saffron
Sage
St. John's Wort
St. Patrick's Leaf
Sandalwood
Sard
Sassafras
Selenite
Smilax
Snakeroot
Sodalite
Spinel
Stevia
Sugulite
Tabak
Tamarisk
Tanzanite
Tarragon
Taxus baccata
Tea Tree
Teazle, common
Tektite
Thimbleberry
Thor's Hat
Thunderegg
Thunderstone
Thymus
Ti
Tiger's Eye
Tin
Titanium
Toadflax
Toadstool
Toloache
Topaz (x3)
Toronjil Morado
Tourmaline
Trefoil
Tribulus
Tsavorite Garnet
Tulip
Turmeric (x2)
Turquoise
Umckaloabo
Unakite
Uranophane
Valeriana wallichii
Vanilla Leaf
Vitex
Vitex negundo
Wahoo
Watermelon Tourmaline
Willow
Wolf's Bane
Wormwood
Xalastocite
Xenotime-Y
Xenotime-Yb
Xonotlite
Yarrow (x2)
Yawroot
Yellow Jasper
Yellow Quartz
Yohimbe
Ylang Ylang
Zauberwurzel
Zea mays
Zebra Agate
Zebra Marble
Zinc
Zircon
Zoisite
Letters never used: J, Q
Letters rarely used: B, C, F, H, I, K, O, P, U, V, W, X, Y