DANBURITE
Hard gemstone suitable for transparent faceted gems but cut only for collectors; colorless crystals abundant from Mexico; rarely, pale yellow waterworn pebbles from gem gravels of Burma.
DATOLITE
Attractive faceted gems cut from very pale yellowish-green crystals; the finest are from Westfield, Massachusetts, and afford flawless gems to 5-6 ct. Unusual massive datolite, colored by copper and other minerals, occurs as warty nodules to 10″ diameter in copper deposits of Michigan; these are prized according to size and color, the least valuable being white, increasing in value toward red, reddish-brown, orange, etc., and sometimes cut for cabochons but mostly sliced and polished as cabinet specimens.
DEMANTOID,   See   GARNET DIAMOND
It is virtually impossible for anyone outside the established diamond cutting, selling, or trading organizations to obtain supplies of gem-quality diamonds except from Brazil, where a substantial quantity of diamonds is produced each year from river gravels by independent miners; the usual sources in Africa are closely controlled by the De Beers Syndicate, which grades the stones and places them on sale in London as lots, each lot containing various sizes and grades according to the established consumption records of the buyers who have traded with the syndicate in the past. Supplies are not abundant and few buyers of lots are willing to part with good stones if they can cut them themselves and realize a greater ultimate profit thereby. This situation, and the necessity for special lapidary equipment in order to cut diamonds, has resulted in few non-professional cutters attempting to cut this gemstone. Prices for rough rise very steeply with
quality and size and the figures given below are only an approximate guide. A full discussion of qualities appears in the next chapter.
DINOSAUR   BONE,   see   QUARTZ DIOPSIDE

Hard, durable, but seldom attractive colors; fairly steady supply of facetable dark green crystals from Madagascar; occasionally in pale green from Alpine localities and New York; also in attractive pale green waterworn crystals from gem gravels of Burma. The Madagascar material is so dark that gems over 5 ct. tend to be unattractive. Star diopside, but very dark, occurs in India.

VIOLANE
Massive, purple variety of diopside, sometimes used in collectors’ cabochons; rare; found in small patches in ore at Franklin, New Jersey, and at St. Marcel, Piemonte, Italy.
Massive, often admixed with other minerals    oz.    .50-.75
DIOPTASE
Vivid emerald-green crystals sometimes faceted into very small gems for col¬lectors; soft, brittle; rarely clean. Largest clear gems about l/£ ct.
Africa, crystal tips to 14″    ct.    .75-1.00
DOLOMITE
An abundant rock-forming mineral, some types of which are used for large objects; rare in clear crystals suitable for faceting; soft, cleavable, a collectors’ gem only.
New Mexico, colorless facet crystals to 15 ct.    ct.    .15-.60
New Hampshire, massive, tan, red & brown    lb.    .75
Michigan, “Kona” dolomite, mottled & colored,
DRAVITE, See TOURMALINE DUMORTIERITE,   See   QUARTZ