The Idea in Brief
When viewed through the lens of Jewish tradition, the suggested literal translation of the verse would appear as follows:
And gold of the land is good: there [one finds] the yellow and the red stone.
The second clause (after the colon) would modify and expand upon the first clause. In this regard, the Babylonian Talmud appears to point to the "yellow stone" (commonly translated as bdellium) and "red stone" (commonly translated as onyx) in this particular verse as references to unalloyed and alloyed gold, respectively.
The cantillation marks of the Masoretic Text would reinforce this Talmudic view. That is, the cantillation marks surrounding "the yellow and the red stone" in the second clause appear to modify the word "gold" in the first clause.
The word of "bdellium" in this verse is בְּדֹלַח, and occurs only twice in the Hebrew Bible (here and in Numbers 11:7). In the latter instance, the reference is to Manna, which appears in that context to be white/yellow in color.
According to Gesenius -
The word for "onyx" in this verse is שֹׁהַם. The color of this stone can be of variant colors to include red (that is, the carnelian stone).
According to the Hebrew Aramaic Lexicon -
Received Oral Jewish Tradition
The Babylonian Talmud contains the received Jewish tradition as understood by the various rabbinic schools during the early and middle ages. The Talmud is a commentary of the Mishnah, which was the starting point for the received oral tradition. The Mishnah provides the two qualitative variants of gold -- pure gold (yellow) and gold alloyed with copper (red).
According to Jacob Neusner's translation of the Mishnah (m. Kippurim 4:4, K-M) -
The rabbis in the early and middle ages took the Mishnah and wrote their analyses and commentaries. These writings were the "Gemara," which, when combined with the Mishnah, formed the Talmud in part as we know today.
The following is Gemara commentary and expansion of the Mishnah (see red box in the image, below) and as translated by Jacob Neusner -
NOTE: The Baker Bible Encyclopedia defines the "Parvaim" as follows:
Geographical area from which Solomon obtained gold for use in the temple (2 Chr 3:6). According to rabbinic sources the gold had a reddish hue, and was used to make the vessel with which the high priest removed the ashes from the altar of burnt offering on the Day of Atonement. Parvaim was probably located in Arabia. (Baker Encyclopedia of the Bible, V.2, p. 1617)
In other words, the Gemara makes reference to Gen 2:12 in order to indicate that there was "yellow gold" and "red gold." Since the "red gold" appeared from Parvaim, this gold was alloyed gold, which, when combined with copper for example, appears red in color. (The implied assumption here is that shovels in the Temple made of pure gold would be too malleable and too heavy to function as effective shovels.) The Talmud therefore seems to make the following distinctions of gold based on the allusion and reference to "yellow" and "red" found in Gen 2:12.
In the next section, the Masoretic Text appears to follow the Talmud. That is, the cantillation marks of the latter half of Gen 2:12 expand and modify the first half of Gen 2:12. Thus the references to yellow and red would modify "gold," which is alloyed (red) and unalloyed (yellow).
Masoretic Cantillation Markings in Relation to the Talmud
The Talmud existed during the early and middle ages (c.200-900 CE), whereas the Masoretic Era appeared later (c.900-1000 CE). Thus the Talmud influenced the Masoretic Text, and not vice-versa. Kelley, Mynatt, and Crawford (1988) indicate the following in this regard.
Thus when we view the cantillation marks in the Masoretic Text for Gen 2:12, the reader notices that the allusion and reference to "yellow and the red stone" are to gold. That is, the stronger disjunctive accents "point" to the logical reading of the Hebrew verse. Please click the image below to enlarge in order to see these contrasts.
The graph above depicts visually through colors how the logic would have "sounded" when sung aloud according to the cantillation marks. That is, chunks of words were modified logically by subsequent words. The second have of the verse therefore modified the first half of the verse, because the "Atnach" accent/cantillation mark appears right after the Hebrew word for "good." When the reader heard that sound (cantillation mark) the logical response was to understand what remained (until the more powerful Silluq appeared and ended the verse). That is, the "Silluq" is the only disjunctive accent which is more powerful than the "Atnach," and therefore everything after "Atnach" is subsumed logically until the "Silluq" appears in the verse (in order to end the verse, since the "Silluq" accent/cantillation mark is only used to end verses). Thus it was not logical for precious gem stones to modify gold in the first half of the verse, but yellow and red to modify gold in the first half of the verse.
In summary, the Masoretic Text provides the literal backdrop to the Talmud, and therefore reinforces the received Jewish Oral Tradition.
The above discussion explanation appears to be how Jewish rabbis and scholars would have approached this verse throughout antiquity. That is, Jewish rabbis and scholars over the millennia passed on what they had received and/or understood as relating to passages of Scripture in the Hebrew Bible. Thus, while the primary interpretation of this verse signals apparent gems and other precious stones ("bdellium and onyx"), Jewish Oral Tradition provides the alternative explanation that refers to the types and varieties of gold ("yellow and red stone").
Elwell, W. A., & Beitzel, B. J. (1988). Baker Encyclopedia of the Bible (Vol. 2). Grand Rapids, MI: Baker Book House, 1617.
Gesenius, W., & Tregelles, S. P. (2003). Gesenius’ Hebrew and Chaldee Lexicon to the Old Testament Scriptures. Bellingham, WA: Logos Bible Software, 103-104.
Kelley, P. H., Mynatt, D. S., & Crawford, T. G. (1998). The Masorah of Biblia Hebraica Stuttgartensia: Introduction and Annotated Glossary. Grand Rapids, MI: William B. Eerdmans Publishing Company, 14.
Koehler, L., Baumgartner, W., Richardson, M. E. ., & Stamm, J. J. (1999). The Hebrew and Aramaic lexicon of the Old Testament (electronic ed.). Leiden; New York: E.J. Brill, 1424.
Neusner, J. (1988). The Mishnah : A New Translation. New Haven, CT: Yale University Press, 271.
Rodkinson, M. L. (Trans.). (1918). The Babylonian Talmud: Original Text, Edited, Corrected, Formulated, and Translated into English (Vol. 6a). Boston, MA: The Talmud Society, 66.