.	Dwarves' Earth Treasures:   Glossary of the Characteristics of Agates & Thundereggs
	.	Amygdaloid (Greek name for "almond shaped") refers to any cavities within any solidified bodies of lava that are formed by the gas bubbles trapped in the lava. Such cavities are typical of basaltic (dark) lava rocks (like Hawaiian volcanoes), but they sometimes also occur in other lava rocks such as rhyolites (typical of volcanoes along mountain ranges). Depending on the thickness of the lava, the shape of cavities tend to egg/almond shaped, irregular shaped, or shaped like a dome with flat bottom.
	.	Lithophysae (Greek name for "Stone Bubbles") is a scientific name for "thundereggs" that refers to the sphere-like bodies in any silica-rich solidified bodies of lava especially rhyolite and perlite (typical of volcanoes along mountain ranges), that had cavities opened within them as a result of release of dissolved gases. The sphere-like bodies lacking any cavities are spherulites which we would tend to call "duds". The cristobalite, a high-temperature polymer (variety) of quartz is the main ingredient in formation of lithophysae. It is common for thundereggs to have ridges.
	.	Concretions refers to the nodules found in the limestones and shales that are formed by the deposition of sediments in the oceans. How the concretions were formed are not well understood, but it seems that with help of water, specific types of minerals like chert align themselves around an object like a fossil or other mineral. In some cases, the fossils like crinoid heads would expand against its host rocks. Eventually, the cavities would form within the concretions as result of the dissolving of weak minerals by water.
	.	Geodes refers to any hollow nodules usually lined with crystals. So it wouldn't be right to call any completely filled nodules "geodes" since they're not hollow at all! It's better to to call any uncut nodules just "nodules" since we don't know what is really inside an uncut rough until we break or cut them.
	.	"Shadowing Effect" (Parallax) refers to the shadows within the transparent films of the agates, which appear and disappear as if "shifting/dancing" when an agate is turned in respect to the light source and viewer.
	.	Sagenite refers to radiating fans of needle-like inclusions within an agate. The needle-like minerals like zeolites formed in the cavities that became sagenite when preserved and replaced by agate.
	.	Chromatography refers to the colors that are not restricted to the films/bands of the agates as if the colors had been spilled over the agate. It is very common for the agates to be porous and that is how many Brazilian Agates can be dyed with unnatural colors.
	.	Plume Agate refers to any agates containing dentritic (fern-like) mineral inclusions within the agates. The iron and manganese minerals tend to be one of the first minerals to grow within a cavity before being covered by agate.
		Waterlines or Onyx Laying refers to any agates containing nearly flat layers of agate or opals giving it an appearance of "waterlines" that has been build up a layer by layer.
		Tillage Agates refers to any agates containing at least one flat layer that is not parallel to the older/lower layers. Such tillaged layering is due to the building up of layers being interrupted by tectonic activities such s faulting. It goes like this: The agate layers were building up a layer by layer in respect to the gravity, and then some earthquake shifted the rock host to a different and tilted position. The layering continued after the event in respect to the gravity.
		Moss Agate refers to any agates containing the strings of mineral inclusions shaped like 'Spanish Moss". The minerals possibly chloride appear to have formed in the solution filled cavities before being covered by agate.
		Iris Agate refers to very thin slices of agates displaying Iris (Rainbow) effect when held in front of a focused light source. Many agate slabs had been mislabeled as "Iris Agate" since they were not showing any rainbow effect at all. The fiber-like structure of Iris Agates were oriented in the certain way that they act like prisms, producing the true Iris Effect.