Diamond open access (OA) is a publishing model that is free for both authors and readers, but their lack of indexing in major bibliographic databases compared to gold journals presents challenges in assessing their uptake. Furthermore, the characteristics of diamond journals, such as language and country of publication, have often been used to support the argument that they are more diverse and serve national research communities. However, there is a notable lack of empirical evidence regarding their geographical and linguistic characteristics. Using the Directory of Open Access Journals (DOAJ) as a benchmark, this paper investigates OA journals through their coverage in OpenAlex, Web of Science (WoS) and Scopus by field, country, language. The results show the lower coverage of diamond journals in WoS and Scopus and confirms the national scope of diamond journals compared to gold. The share of English-only journals is considerably higher among gold journals in every database. High-income countries have the highest share of authorship in every domain and type of journal, except for diamond journals in the social sciences and humanities. Understanding the current landscape of diamond OA indexing can aid the scholarly communications community and decision-makers in advancing policy and practices toward more inclusive OA models.

The last decade of altmetrics research has demonstrated that altmetrics have a low to moderate correlation with citations, depending on the platform and the discipline, among other factors. Most past studies used academic works as their unit of analysis to determine whether the attention they received on Twitter was a good predictor of academic engagement. Our work revisits the relationship between tweets and citations where the tweet itself is the unit of analysis, and the question is to determine if, at the individual level, the act of tweeting an academic work can shed light on the likelihood of the act of citing that same work. We model this relationship by considering the research activity of the tweeter and its relationship to the tweeted work. The results show that tweeters are more likely to cite works affiliated with their same institution, works published in journals in which they also have published, and works in which they hold authorship. It finds that the older the academic age of a tweeter the less likely they are to cite what they tweet, though there is a positive relationship between citations and the number of works they have published and references they have accumulated over time.