The twelve gates of the New Jerusalem, which will be made by God, are stated to be composed of margarites (Revelation 21:21), a Greek word (Strong's Concordance #G3135) both Strong's and Thayer's lexicon render as "pearl." All ten versions of God's word used in this series also translate this word as referring to this natural precious stone. Modern cultural references to the "pearly gates" of heaven are based on this scriptural verse.
In the Old Testament, Job states that the gaining of wisdom is more precious than gabiysh (Strong's #H1378). This Hebrew word comes from an unused root that means, "to freeze" or "crystal" (from its resemblance to ice) which Strong's translates as "pearls."
Although the KJV translates gabiysh as "pearls" in Job 28:18, many other translations render the word as "crystal." Interestingly, the natural gemstone still shows up in this quote, as several Bibles (ESV, HCSB and NASB) translate the Hebrew paniyn (Strong's #H6443), found at the end of the verse, as "pearls" as seen below.
18 No mention shall be made of coral or of crystal (Hebrew gabiysh); the price of wisdom is above pearls (Hebrew paniyn - Job 28:18, ESV).
Pearls are the second most named gemstone in the entire KJV, primarily due to its New Testament references. It is also one of the two major gems in Scripture that are produced organically (the other being coral) as opposed to inorganically.
Natural pearls, which are composed primarily of calcium carbonate, are created within the soft tissue of living shelled mollusks (usually clams). Anciently, because they were rare to find, many oysters had to be gathered and opened (thus killing them) in order to find one of these gems. One modern method for making these gemstones more available is producing them in farms that use human as well as natural processes to create them.
Pearls can be not only round but also pear, egg, and other shapes. While white is the most familiar coloration of this gemstone, they can also come in other colors such as light rose, black, blue, red, and violet. Their rarity makes them perfect to use in one of Jesus's most well known parables.
45. Again, the kingdom of heaven is compared to a merchant seeking beautiful pearls; 46. Who, after finding one very precious pearl, went and sold everything that he had, and bought it (Matthew 13:45 - 46, HBFV)
This natural gem has been prized for its beauty for a long time, having been known in China for more than 4,000 years (Diamonds, Pearls and Precious Stones, page 42).
The natural gem was associated with the moon and Monday. In dreams, this gemstone was believed to symbolize faithful friends. They were also considered, in some cultures, as the tears of the gods. Pearls were also considered the talismanic stones of Sunday (Curious Lore of Precious Stones, page 30, 332, 358).
The second stone mentioned in the breastplate (Exodus 28:17) is called in the Hebrew pitdah (Strong's #H6357), which Strong's translates as a topaz and the BDB lexicon states either refers to a topaz or a chrysolite. The same word is also used to refer to the second stone that decorated Lucifer (Ezekiel 28:13). Nine out of the ten Scriptural versions used in the series translate pitdah in Exodus 28:17 and Ezekiel 28:13 as topaz, while the NLT calls it "a pale green peridot."
Research seems to indicate, however, that pitdah, concerning the priest's breastplate, refers instead to a peridot and not a topaz.
"The topaz of the ancients was unquestionably the gem commonly called chrysolite at present (olivine, peridot) . . . There seems to be little doubt that this is the topazius of ancient writers, which usually signified our chrysolite, or peridot, not our topaz; for Pliny and his successors describe the topazius as a stone of a greenish hue" (Curious Lore of Precious Stones, pages 66, 291)
"True topaz is an aluminum floro silicate and quite hard, but the Old Testament topaz may refer to peridot, a magnesium olivine" (Holman Bible Dictionary)
"In biblical times topaz was a very highly prized gem . . . However, the gems spoken of under this name were probably chrysolite . . ." (Diamonds, Pearls and Precious Stones, page 86)
The view that this breastplate stone is likely a peridot, and not a topaz, is also argued by commentaries such as the IBSE and the Bible Background Commentary. The book "Gemstones in the Breastplate" also makes the case that the second stone in the breastplate is this stone. The book's reasons (among others) for this conclusion is that it has a long history of use as jewelry and were, at one time, valued more than diamonds (page 15).
Given the difficulty to engrave such a hard stone as topaz it seems likely that the breastplate stone called pitdah is best translated as peridot gemstones. True topaz, however, was likely used to adorn Lucifer and will be used in the New Jerusalem.
According to the mindat.org site, the modern term "chrysolite" is used as a synonym of the olivine (peridot). This gemstone only exists in variations of an olive-green color.
Peridot, if worn in a setting of gold, was believed to dispel "the terrors" of the night. It could be used as protection against evil spirits and even chase them away (Curious Lore of Precious Stones, page 67).